Altitudinal Variation of Antioxidant Components and Capability in Indocalamus Latifolius (Keng) Mcclure Leaf

J Nutr Sci Vitaminol, 59, 336–342, 2013

Altitudinal Variation of Antioxidant Components and Capability in Indocalamus latifolius (Keng) McClure Leaf

Qinxue Ni1, Zhiqiang Wang1, Guangzhi Xu1, Qianxin Gao1, Dongdong Yang1, Fumiki Morimatsu2 and Youzuo Zhang1,*

1 The Key Laboratory for Quality Improvement of Agricultural Products of Zhejiang Province, Zhejiang Agriculture and Forestry University, Lin’an 311300, China 2 R & D Center, Nippon Meat Packers Inc., Tsukuba, Ibaraki 300–2646, Japan (Received February 7, 2013)

Summary Indocalamus latifolius (Keng) McClure leaf is a popular food material in East Asia due to its antioxidant and anticorrosive activities. To utilize it more effectively, we investigated the discrepancy of antioxidant activities and active compound content in Indocala- mus latifolius leaf along with the altitude change. Total flavonoids, phenolics, titerpenoids and eight characteristic active constituents, i.e, orientin, isoorientin, vitexin, homovitexin, p-coumaric acid, chlorogenic acid, caffeic acid, and ferulic acid, were determined by UV- spectrophotometer and synchronous RP-HPLC, respectively. Antioxidant activity was measured using DPPH and FRAP methods. Our data showed that the content of TP and TF, DPPH radical scavenging ability and ferric reduction power of Indocalamus latifolius leaf changed as altitude altered, with the trends of decreasing gradually when lower than 700 m and then increasing to 1,000 m. Chlorogenic acid and orientin were the main characteristic compounds in Indocalamus latifolius leaf and were also affected by altitude. Our result indicated that higher altitude with an adverse environment is conducive to secondary metabolite accumulation for Indocalamus latifolius. It would provide a theoretical basis to regulate the leaf collection conditions in the industrial use of Indocalamus latifolius leaf. Key Words Indocalamus latifolius (Keng) McClure, altitude, secondary metabolites, bamboo characteristic compounds, antioxidant activities

Bamboo is an evergreen and perennial plant of the latifolius leaves are mainly attributable to its abundant Gramineae family, which has a tropical and subtropical secondary metabolites, such as flavonoids, phenolic distribution. It is one of the most primitive and diverse components and triterpenoid (5). Among them, orien- taxa in the world and widely used as an important com- tin, isoorientin, vitexin, homovitexin, chlorogenic acid, modity in Southeast Asia and pacific islands, for exam- caffeic acid, p-coumaric acid and ferulic acid are eight ple, as building material, handicraft articles, food mate- characteristic compounds in bamboo leaves and were rial and traditional medicine. In particular, bamboo confirmed with antioxidant, anti-cancer, anti-inflam- leaves have been used in traditional Chinese medicine mation and radioprotective activities (6–10) (Fig. 1). for over 1,000 y for the treatment of fever, inflamma- Secondary metabolites are the major ingredients tion and detoxification. To date, bamboo leaf extracts that have been associated with the biological activity have also been used in food additives and pharmaceu- of plants. Their synthesis and accumulation pathways tical products, mainly to lessen or cure stomachache, in plants are the results of long-term natural selection diarrhea, vomiting, restlessness and excessive thirst (1, under certain conditions, which are closely related to 2). the ecological environment. The composition and con- Indocalamus latifolius (Keng) McClure is a kind of tents of secondary metabolites in the same plant show bamboo grass with a large leaf and dwarf stalk, which a significant difference in different ecological environ- is widely distributed in the south of China. Because of ments (11, 12). Altitude is an important environmen- its advantages of large biomass, easy collection and tal factor that affects the accumulation of secondary various biological activities, the leaves have been used metabolites due to the change of light, temperature, as the wrap of rice tamale, a popular traditional Chi- moisture and other ecological factors. The valid impact nese food, for several thousand years. It can make rice of altitude on the content of secondary metabolites has be more fragrant, less prone to rancidness and healthful been confirmed by several studies (13, 14). by its aroma components and antibacterial, antioxidant Yet, till now, the changes in secondary metabolite compounds (3, 4). Our previous study revealed that the composition and content and the physiological activities biological activities and functions of the Indocalamus of Indocalamus latifolius leaf along the altitudinal gradi- ent have rarely been reported. In order to improve the * To whom correspondence should be addressed. comprehensive utilization of bamboo leaf, the present E-mail: [email protected] study investigated the altitude variation of the total level

336 Altitudinal Variation of Antioxidant Composition in Bamboo Leaf 337

University. All samples from each altitude were investigated three times in order to decrease method-related measurement errors. The characteristics of the collection site where Indo- calamus latifolius grows need to be commented on. Mt. Longwang is located between Zhejiang and Anhui Prov- inces in the southeast of China (1,587.4 m elevation, (A) 30˚23′N, 119˚23′E), which could be characterized as a subtropical monsoon area. The average temperature R: from the foothills and hilltop is 15.1–8.9˚C. The temperature at lower altitudes would decrease by 0.48˚C per 100 m. Extreme maximal and minimal temperature registered in summer and winter of the year were 37˚C and 211.3–20.6˚C, respectively. The frost-free period through the year lasted 208 d with a precipitation (B) 1,647 mm/y and average annual sunshine of 1,550– 2,000 h around the whole mountain. The annual Flavonoids R1 R2 R3 Phenolic acids R4 R5 UV- irradiation on the region was stronger in spring- Orientin -H -Glu -OH Chlorogenic acid -OH -R summer than that in autumn-winter with an annual 2 Homoorientin -Glu -H -OH Caffeic acid -OH -OH UV-irradiation of about 150 MJ/m . Vitexin -H -Glu -H p-Coumaric acid -H -OH Extraction process. Bamboo leaves were washed, Isovitexin -Glu -H -H Ferulic acid -OCH3 -OH drained, and enzymes inactivated immediately (micro- wave treated at 640 W three times: 1 min each time), Fig. 1. Chemical structure of orientin, homoorientin, then dried in a vacuum drying oven (60˚C or 2 h). vitexin, isovitexin, chlorogenic acid, caffeic acid, p-coumaric acid, and ferulic acid. (A) is the basic framework The dried bamboo leaves were then milled to a powder of 4 flavonoids; (B) is the basic framework of 4 phenolic of 40-mesh particle size. Bamboo leaf powder 1 g was acids. mixed with 150 mL ethanol-aqueous solution (70%, v/v), refluxed 3 times (2 h each time), filtered and evap- orated to a constant volume of 100 mL. The moisture content of each sample was measured with an infra- of phenolics (TP), flavonoids (TF) and triterpenoid (TT), red moisture analyzer (Ohaus, Pine Brook, NJ) before plus eight characteristic compounds in bamboo leaf, extraction, and all the results were calculated based on in addition to antioxidant activities. Simultaneously, dry materials. we also discussed the relationship between antioxidant Determination of total phenolic (TP), total flavonoid (TF) activity and secondary metabolites with the aim of pro- and total triterpenes (TT) content. The contents of total viding a theoretical basis for exploiting and managing phenolics (TP), total flavonoids (TF) and triterpenoids bamboo leaf resources more scientifically and efficiently. (TT) in Indocalamus latifolius leaf were investigated using spectrophotometer analyses methods as reported below MATERIALS AND METHODS (15). All measurements were reproduced in triplicate. Chemical reagents. Methanol (HPLC grade), aceto- The TP concentration of the samples was determined nitrile (HPLC grade), Folin-Ciocalteau reagent, vanillin, using the Folin-Ciocalteu colorimetric method. The diphenyl-2-picryl-hydrazyl (DPPH), tripyridyltriazine amount of TP was calculated as a p-hydroxybenzoic (TPTZ) and authentic standards of phenolic compounds acid equivalent from the standard curve (Y52.2582 (p-hydroxybenzoic acid, chlorogenic acid, caffeic acid, X10.037, r50.9989), and expressed as the percentage p-coumaric acid, ferulic acid) were purchased from of p-hydroxybenzoic acid in dry leaf weight (%, DW). Sigma-Aldrich Co. (St. Louis, MO). Authentic standards The aluminum nitrate-sodium nitrite colorimetric of flavonoids (rutin, orientin, isoorientin, vitexin, homo- method was used to determine the TF content of the sam- vitexin) were purchased from Extrasynthese Chemical ples. The amount of TF was calculated as a rutin equiv- S.A.S. (Lyon Nord, Genay Cedex, France). Other chemi- alent from the standard curve (Y50.014X10.0016, cals were of analytic grade. r50.9999), and expressed as the percentage of rutin in Plant material and collection site. Indocalamus lati- dry leaf weight (%, DW). folius leaves were collected from Mt. Longwang (An’Ji, The vanillin-glacial acetic acid colorimetric method Zhejiang Province, China) at different altitudes (100, was used to determine the TT concentration of samples. 300, 500, 700 and 1,000 m) on 17th May, 2011, on a The amount of TT was calculated as an ursolic acid equiv- sunny day at the temperature of 12–20˚C, and average alent from the standard curve (Y50.0048X20.0136, relative humidity of 54% . Three sample plots were ran- r50.9976), and expressed as the percentage of ursolic domly chosen at each altitude. Leaves were picked ran- acid in dry leaf weight (%, DW). domly from different branches in each sample plot. Indo- Assay of DPPH free radical scavenging activity. The calamus latifolius were identified by bamboo taxonomy DPPH free radical scavenging activity of the samples expert Wei Fang of Zhejiang Agriculture and Forestry was measured using the method of Brand-Williams et 338 Ni Q et al. al. (16) and Uluata and Ozdemir (17) with some modi- by HPLC. Curves of eight standard compounds using fications. The absorbance at 517 nm was measured concentration as abscissa and peak area as the vertical 1 h after mixing 0.1 mL of samples with 3.9 mL DPPH axis were charted (chlorogenic acid, RT (retention time): solution (0.10 mmol/L), using a T60 UV-vis spectropho- 7.81 min, Y5705.11X132.347, r50.9951; caffeic tometer (Beijing Purkinje General Instrument Co., Ltd., acid, RT: 11.9 min, Y52943X167.087, r50.9955; Beijing, China) using methanol as a blank. The DPPH isoorientin, RT: 15.9 min, Y5251.08X14.1889, r5 radical scavenging rate (%) was calculated in the fol- 0.9949; orientin, RT: 17.3 min, Y5253.47X112.283, lowing way: % radical scavenging rate5(Ablank2Asample)/ r50.9995; p-coumaric acid, RT: 21.0 min, Y5 Ablank3100, where Ablank is the absorbance of the blank 2979.3X26.5085, r50.9992; vitexin, RT: 23.0 min, reaction, and Asample is the absorbance of samples. The Y51488.2X111.022, r50.9988; homovitexin, RT: results were expressed as IC50 of DPPH radical scaveng- 23.6 min, Y51297.3X111.646, r50.9998; ferulic ing, where IC50 means the amount of antioxidant nec- acid, RT: 23.9 min, Y54149.7X127.76, r50.9959). essary to decrease the initial concentration of DPPH All the samples were then passed through a 0.45 mm fil- radical (0.10 mmol/L) by 50%. All measurements were ter and analyzed directly by HPLC. The amount of each reproduced in triplicate. compound in the bamboo leaves was calculated accord- Assay of ferric reducing antioxidant power (FRAP). ing to the standard curves. FRAP assay was performed following Benzie and Strain Statistical analysis. Mean values and standard devia- (18) and Liao et al. (19) with minor modifications. It is tions were calculated from the data obtained from three the method of measuring the samples to reduce Fe31– samples at each height. All the results are given as Fe21. Briefly, 0.3 mL of sample solution (300 mg/mL) mean6standard deviation (SD). Data were analyzed by was mixed with 2.7 mL of FRAP reagent, which con- one-way analysis of variance (ANOVA). Significant dif- tained 2.5 mL of 10 mmol/L tripyridyltriazine (TPTZ) ferences were assessed with the LSD test (p,0.05). The solution in 40 mmol/L HCl, plus 2.5 mL of 20 mmol/L statistical analysis was performed using the data collec- FeCl3 and 25 mL of 0.3 mol/L acetate buffer, pH 3.6. tion program, SPSS 19.0. The absorption of the reaction mixture was mea- RESULTs AND DISCUSSION sured at 593 nm. Methanol (0.3 mL) and 2.7 mL TPTZ reagent mixture was used as a blank. Aqueous solu- Altitude variation of active compounds in Indocalamus lati- tions of known Fe(II) concentration, in the range of folius leaf 0–1,000 mmol/L (FeSO4), were used for obtaining the TP, TF and TT with several biological activities are the calibration curve. Triplicate tubes were prepared for major active compounds in bamboo leaf. Their contents each sample. The reducing power of each sample was in Indocalamus latifolius leaf are varied with altitude expressed as an equivalent concentration of FeSO4. This changes as Fig. 2 shows. FRAP parameter was defined as the concentration of With the elevation increasing, the TF and TP con- antioxidant having a ferric reducing ability equivalent tent in Indocalamus latifolius leaf showed a significant to that of 1 mmol FeSO4. and nonlinear altitudinal tread, with them declining Determination of the content of eight bamboo charac- below about 700 m and then increasing. Indocalamus teristic compounds by RP-HPLC. The contents of eight latifolius leaf contained significantly higher TF con- bamboo characteristic compounds in bamboo leaf, i.e. tent at 1,000 m (0.7760.04%) than at other altitudes orientin, isoorientin, vitexin, homovitexin, chlorogenic and TP content at 1,000 m and 100 m (3.3660.11%, acid, caffeic acid, p-coumaric acid and ferulic acid, were 3.3060.20%, respectively) (p,0.05). The lowest analyzed using an HPLC system (consisting of a vac- level of TF and TP content both appeared at 700 m uum degasser, an auto-sampler, a quaternary pump, (0.4760.04%, 2.4160.17%, respectively). TT content and diode array detector; Agilent Series 1200, Agi- was also dependent on the altitude, generally decreas- lent Technologies Inc., Palo Alto, CA) equipped with a ing gradually as the altitude increased. reversed-phase C18 analytical column of 4.63250 mm The composition and content of secondary metabo- and 5 mm particle size (Inertsil® ODS-SP). The column lites in plants are affected by several meteorological fac- temperature was maintained at 40˚C. The injection tors, such as temperature, moisture, and light. Different volume was 10 mL. The mobile phase was acetonitrile climate environments at certain altitudes caused the (A), 1% acetic acid aqueous solution (B). The optimized discrepancy in the amount of the active compounds in chromatographic condition was: 0–15 min, A 15%, B Indocalamus latifolius leaf (20). Furthermore, under nor- 85%; 15–25 min, A 15–40%, B 85–60%; 25–34 min, mal conditions, Indocalamus latifolius began sprouting A 40%, B 60%; 34–40 min, A 40–15%, B 60–85%; a during March to April, and then grew very fast from mid- 5 min post-run was used after each analysis. The flow or late April. Secondary metabolites began to accumu- rate used was 0.8 mL/min. late in May. Yet, each phenological phase of Indocalamus The standard solution containing orientin, isoorien- latifolius was delayed about 10–15 d for every increased tin, vitexin, homovitexin, chlorogenic acid, caffeic acid, experimental altitude on Mt. Longwang mainly because p-coumaric acid and ferulic acid was prepared with 50% of the temperature decreasing with elevation increas- methanol-aqueous. After dilution to make solutions of ing. Indocalamus latifolius leaves in our research were 5 different concentrations, the standard solution was collected in May, when Indocalamus latifolius at a lower filtered through a 0.45 mm filter and analyzed directly altitude (100 m) was already beginning to accumulate Altitudinal Variation of Antioxidant Composition in Bamboo Leaf 339

4.50 c 4.00 c c,d b 3.50 d bc b a a 3.00

,DW) a 2.50 TF (% t TP en 2.00 nt TT

Co 1.50

1.00 bbb c a 0.50

0.00 100 300 500700 1000 Height of atitude (m)

Fig. 2. The tendency of active compound contents in Indocalamus latifolius leaf with altitude variation (n53). Different lowercase letters mean significant difference (p,0.05).

500.00 1.00 c

) 400.00 0.80

l/L b b b b mo

( 300.00 0.60 b b a e

lu a a Va 200.00 0.40 AP FR 100.00 0.20 IC50 on DPPH(mg/mL)

0.00 0.00 100 300 500700 1000 Height of altitued (m) FRAP assay DPPH scaenging ability

Fig. 3. The tendency of antioxidant activities of Indocalamus latifolius leaf with altitude variation (n53). Different lowercase letters mean significant difference (p,0.05). secondary metabolites, so active compounds were at a logical value to the plant were required. This may also high level. In contrast, Indocalamus latifolius at a higher be a reason for Indocalamus latifolius leaf containing the altitude (lower than 700 m) were still in the stage of highest level of active compounds at 1,000 m. sprouting or fast-growth due to the delay of phenophase Altitudinal variation in antioxidant activities of Indocala- with increased elevation. Primary metabolism played mus latifolius leaf the major role in the plant at these phenophases (21, Antioxidant activity, in terms of DPPH assay and 22). Thus, active compound content in Indocalamus lati- FRAP assay, were measured in the present study using folius leaf decreased gradually until 700 m. Yet, with the spectrophotometric methods. elevation continuing to increase, secondary metabolites DPPH radical scavenging ability of Indocalamus latifo- accumulated the previous year were still kept at a high lius leaf extracts from different altitudes were expressed level for Indocalamus latifolius rhizomes that had not yet as IC50 (Fig. 3), which represents the antioxidant con- begun to sprout. So their active compounds showed the centration necessary to reduce the initial DPPH con- highest level at 1,000 m. The phenomenon is in line centration by 50%. Lower IC50 indicated better DPPH with a study which reported that phenological phases radical scavenging ability. With the increased in eleva- of plants will be delayed due to the temperature drop tion, the DPPH radical scavenging IC50 first increased 0.5–0.6˚C for every 100 m altitude rise (20). and then decreased. Samples collected from 100 and With the elevation increasing, atmospheric density 1,000 m showed significantly higher ability than the will decrease and light intensity (especially the UV-B) others (p,0.05). The sequence of DPPH radical scav- increase (23). The fact of UV-B-induced changes in a enging ability was as follows: 1,000 m.100 m.500 m range of different plant metabolites, including antioxi- .300 m.700 m. dants, alkaloids and isoprenoids, was verified in the field The trend of ferric reducing antioxidant power of in studies which focused on the accumulation of phe- Indocalamus latifolius leaf extracts with altitude increase nolic compounds (24–27). Under stressful conditions, was similar with that of DPPH radical scavenging abil- extra compounds with nutritional and/or pharmaco- ity. The sequence of reducing power was as follows: 340 Ni Q et al.

0.80

) 0.70 mL

g/ 0.60 r = 0.7257** TF (m 0.50 r = 0.0034

PH r = 0.5543** 0.40 TP

DP (A)

on 0.30

50 0.20 TT IC 0.10 0.00 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 Antioxidants content (%)

450.00 400.00

l/ L) 350.00 r = 0.8336** mo 300.00 TF

( r= 0.0075

e 250.00 r = 0.8537**

lu TP 200.00

Va (B)

150.00 TT AP 100.00 FR 50.00 0.00 0.00 1.00 2.00 3.00 4.00 5.00 Antioxidants content (%) * p < 0.05; ** p < 0.01.

Fig. 4. Correlation analyses TF, TP, TT and IC50 on DPPH (A) and FRAP value (B).

Table 1. Altitude variation of 8 characteristic compounds (n53).

Chlorogenic p-Coumaric Altitude Caffeic acid Homoorientin Orientin Vitexin Isovitexin ferulic acid acid acid (m) (mg·g21) (mg·g21) (mg·g21) (mg·g21) (mg·g21) (mg·g21) (mg·g21) (mg·g21)

100 1,170b650 56.0c62.3 416b620 1,450a660 152e66 477b622 120b65 3.22d60.15 300 1,170b650 59.8b,c6 2.7 429b617 1,320b660 255c611 498b623 110c64 4.29c60.17 500 689c632 61.7b62.5 432b619 1,300b670 202d610 425c620 112b,c64 9.59a60.42 700 623c634 59.1b,c6 2.1 369c615 1,190c650 275b612 256d610 90.9d64.2 4.75b60.23 1,000 1,490a660 81.8a63.5 887a626 422d618 324a614 920a643 137a66 2.70e60.15

Values in same row followed with different letters mean significant difference (p,0.05).

1,000 m.100 m.300 m.500 m.700 m. The reduc- acid, p-coumaric acid, orientin, isoorientin, vitexin, and ing power of samples from 1,000 m was significantly homovitexin, as shown in Table 1. HPLC chromato- higher than others’ (p,0.05). grams are shown in Fig. 5. Correlation analysis As shown in Table 1, there are significant effects of Many studies showed TP, TF and TT correlations altitude variation on the content of characteristic com- with antioxidant properties (28–30). The correlations pounds. Among 4 characteristic flavonoids, the content between antioxidant components and antioxidant activ- of orientin is significantly higher than the others’, but ity were also analyzed using Pearson correlation coeffi- the variation tendency is contrary to the trend of the cients in the present study (Fig. 4). The correlation coef- TF and other flavonoids. The highest level appeared at ficient between TF, TP, TT and DPPH radical scavenging 100 m in contrast to the lowest at 1,000 m. The varia- is TP.TF.. TT, which means TP in Indocalamus latifolius tion tendency of isoorientin, vitexin and homovitexin leaf plays a leading role in the ability of DPPH radical contents are similar to that of TF: the highest level scavenging. TF in Indocalamus latifolius leaf is the main appeared at 1,000 m and the lowest appeared at 700 m. active compound related to FRAP assay, with the cor- As for the four phenolic acids, chlorogenic acid is the relation coefficient of 0.8537. main phenolic acid in Indocalamus latifolius leaf. The RP-HPLC analysis of eight characteristics compounds in content of chlorogenic acid at different altitudes was Indocalamus latifolius leaf similar to the TP tendency, ranging from 623.27 mg/g RP-HPLC parameters were optimized to analyze alti- (700 m) to 1,485.04 mg/g (1,000 m). p-Coumaric acid tudinal variation of eight characteristic compounds in content also peaked at 1,000 m. Caffeic acid showed bamboo leaf, i.e., chlorogenic acid, caffeic acid, ferulic slight changes with altitudinal variations and there was Altitudinal Variation of Antioxidant Composition in Bamboo Leaf 341

(A)

(B)

Fig. 5. HPLC chromatograms of standard solution and extracts of bamboo leaves. (A) Standard solution; (B) Sample of 1,000 m. 1: chlrogenic acid; 2: caffeic acid; 3: isoorientin; 4: orientin; 5: p-coumaric acid; 6: vitexin; 7: homovitexin; 8: ferulic acid. little ferulic acid contained in Indocalamus latifolius leaf. and plant phenophase delay along with the eleva- Furthermore, according to the results, the eight tion increase may cause these changes. The phenom- characteristic phenolic compounds exist in Indocalamus enon of active components in Indocalamus latifolius leaf latifolius leaf at remarkably lower levels than in other increased dramatically at high altitude, indicating the reported bamboo grass leaves, such as Sasa argenteast- excellent antioxidant protection system of plants in riatu, Shibataea chinensis, Pleioblastus kongosanensis f. an adverse environment. This physiological metabolic aureostriatus, S. pygmaea and S. veitchii (5). However, mechanism might be the result of the long-term abiotic because of its advantage of large leaves, easy collection stresses effect of plants. and convenient use, it was selected as the wrap of rice tamale, a popular traditional Chinese food, for several Acknowledgments thousands years. Thus, besides Indocalamus latifolius, Financial support from Public Agricultural Research other bamboo grasses, in our opinion, which have the Projects of Zhejiang Province (2011C32G2100046) is potential to be developed as leafy bamboo groves, are gratefully acknowledged. also worth further study. REFERENCES CONCLUSION 1) Lu B, Wu X, Zhang Y. 2005. Advances in studies on anti- The results in the present study showed that the con- oxidative activity and cardio-cerebrovascular pharma- tent of TP, TF and antioxidant capabilities (DPPH assay cology of bamboo-leaf-flavonoids. Chem Ind Forest Prod 25: 120–124. and FRAP assay) change as a result of altitude changes 2) Choi DB, Cho KA, Na MS, Choi HS, Kim YO, Lim DH, Cho due to a series of environment factors. Generally, their SJ, Cho H. 2008. Effect of bamboo oil on antioxidative trends were all to decrease gradually under 700 m and activity and nitrite scavenging activity. J Ind Eng Chem then increase to 1,000 m. Correlation analysis showed 14: 765–770. TP in Indocalamus latifolius leaf plays a leading role in 3) Zhang Y. 1997. Analysis on the chemical components the ability of DPPH radical scavenging, whereas FRAP in the essential oil and headspace volatile of bamboo relies mainly on TF. Among the eight bamboo char- leaves. Res Dev Nat Prod 10(4): 38–44. acteristic compounds, chlorogenic acid and orientin 4) Li SF, Dai Y, Li JJ. 2010. Comparison of scavenging DPPH accounted for the largest share of Indocalamus latifolius free radical and restraining bacteria of Indocalamus lati- leaf extract and also varied with altitude changes. UV-B folius leaf’s extracts. Food Sci Technol 35(4): 174–177. radiation enhancement, illumination time increase 5) Ni Q, Liu Y, Gong L, Lin X, Fang W, Zhang Y. 2011. 342 Ni Q et al.

Active components in six kinds of ground bamboo leaves 18) Benzie IF, Strain JJ. 1996. The ferric ablilty of plasma as and their anti-oxidant activities. Chin Trad Herbal Drugs measure of antioxidant power: the FRAP method. Anal 42: 2317–2321. Biochem 239: 70–76. 6) Chen JH, Ho CT. 1997. Antioxidant activities of caffeic 19) Liao H, Liu H, Yuan K. 2012. A new flavonol glycoside acid and its related hydroxycinnamic acid compounds. J from the Abelmoschus esculentus Linn. Pharmacogn Mag Agric Food Chem 45: 2374–2378. 8(29): 12–15. 7) Devi PU, Bisht KS, Vinitha M. 1998. A comparative 20) Körner C. 2003. Alpine Plant Life: Functional Plant study of radioprotection by Ocimum flavonoids and syn- Ecology of High Mountain Ecosystems, 2nd ed. Springer thetic aminothiol protectors in the mouse. Brit J Radiol Berlin Heidelberg, New York. 71(847): 782–784. 21) Toor PK, Savage GP, Lister CE. 2006. Seasonal variations 8) Manthey JA, Guthrie N. 2002. Antiproliferative activi- in the antioxidant composition of greenhouse grown ties of citrus flavonoids against six human cancer cell tomatoes. J Food Compos Anal 19: 1–10. lines. J Agric Food Chem 50: 5837–5843. 22) Raffo A, Malfa GL, Fogliano V, Mmiani G, Quaglia G. 9) Zhang Y, Jiao J, Liu C, Wu X, Zhang Y. 2008. Isolation 2006. Seasonal variations in antioxidant components and purification of four flavone C-glycosides from anti- of cherry tomatoes (Lycopersicon esculentum cv. Naomi oxidant of bamboo leaves by macroporous resin column F1). J Food Compos Anal 19: 11–19. chromatography and preparative high-performance liq- 23) McKenzie RL, Aucamp PJ, Bais AF, Björn LO, Ilyas M. uid chromatography. Food Chem 107: 1326–1336. 2007. Changes in biologically-active ultraviolet radia- 10) Kang J, Li ZM, Wu T, Jensen GS, Schauss AG, Wu XL. tion reaching the earth’s surface. Photochem Photobiol 2010. Anti-oxidant capacities of flavonoid compounds Sci 6: 218–231. isolated from acai pulp (Euterpe oleracea Mart.). Food 24) Hollosy F. 2002. Effects of ultraviolet radiation on plant Chem 122: 610–617. cells. Micron 33: 179–197. 11) Pirie A, Parsons D, Renggli J, Narkowicz C, Jacobson GA, 25) Livanos P, Apostolakos P, Galatis B. 2012. Plant cell divi- Shabala S. 2013. Modulation of flavonoid and tannin sion: ROS homeostasis is required. Plant Signal Behav 7: production of Carpobrotus rossii by environmental con- 771–778. ditions. Environ Exp Bot 87: 19–31. 26) Redha A, Patrice S, Al-Hasan R, Afzal M. 2013. Cono- 12) Selmar D, Kleinwachter M. 2013. Influencing the prod- carpus lancifolius biochemical responses to variable UV- uct quality by deliberately applying drought stress dur- Birradiation. Biochem Syst Ecol 48: 157–162. ing the cultivation of medicinal plants. Ind Crop Prod 42: 27) Jansen MAK, Hectors K, O’Brien NM, Guisez Y, Potters 558–566. G. 2008. Plant stress and human health: Do human 13) Mcdougal KM, Parks CR. 1984. Elevational variation in consumers benefit from UV-B acclimated crops?Plant Sci foliar flavonoids of Quercus rubra L. (Fagaceae). Am J Bot 175: 449–458. 71: 301–308. 28) Smina TP, Mathew J, Janardhanan KK, Devasagayam TP. 14) Nikolova MT, Ivancheva SV. 2005. Quantitative fla- 2011. Antioxidant activity and toxicity profile of total vonoid variations of Artemisia vulgaris L. and Veronica triterpenes isolated from Ganoderma lucidum (Fr.) P. Karst chamaedrys L. in relation to altitude and polluted envi- occurring in South India. Environ Toxicol Pharmacol 32: ronment. Acta Biol Szegediensis 49(3–4): 29–32. 438–446. 15) Ni Q, Xu G, Wang Z, Gao Q, Wang S, Zhang Y. 2012. 29) Zhang G, He L, Hu M. 2011. Optimized ultrasonic- Seasonal variations of the antioxidant composition in assisted extraction of flavonoids from Prunella vulgaris ground bamboo Sasa argenteastriatus leaves. Int J Mol Sci L. and evaluation of antioxidant activities in vitro. Innov 13: 2249–2262. Food Sci Emerg Techonol 12: 18–25. 16) Brand-Williams W, Cuvelier ME, Berset C. 1995. Use of 30) Kunyanga CN, Imungi JK, Okoth MW, Biesalski HK, a free radical method to evaluate antioxidant activity. Vadivel V. 2012. Total phenolic content, antioxidant and LWT Food Sci Technol 28: 25–30. antidiabetic properties of methanolic extract of raw and 17) Uluata S, Ozdemir N. 2012. Antioxidant activities and traditionally processed Kenyan indigenous food ingredi- oxidative stabilities of some unconventional oilseeds. J ents. LWT Food Sci Technol 45: 269–276. Am Oil Chem Soc 89: 551–559.