Short Communication Environ. Control Biol., 55 (3), 143
145, 2017 DOI: 10.2525/ecb.54.143 Screening the Allelopathic Activity of 14 Medicinal Plants from Northern Thailand

1 3 2 1 3 Prapaipit SUWITCHAYANON , , Kaewalin KUNASAKDAKUL and Hisashi KATO-NOGUCHI ,

1 Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki, Kagawa 761
0795, Japan 2 Department of Entomology and Plant Pathology, Faculty of Agriculture, Chiang Mai University, Chiang Mai 50200, Thailand 3 The United Graduate School of Agricultural Sciences, Ehime University, 3
5
7 Tarumi, Matsuyama, Ehime 790
8566, Japan

(Received December 7, 2016; Accepted April 5, 2017)

Fourteen medicinal plants from northern Thailand, which dominate and form large colonies, were dried, powdered, and evaluated for growth inhibitory activity using a modified sandwich method. All the plants showed inhibitory activities on the growth of lettuce seedlings: Cymbopogon nardus had the strongest activity, completely inhibiting the growth of the let- tuce hypocotyls and radicles; Piper retrofractum completely inhibited the hypocotyl growth and 93.5% of the radicle growth; and the remaining plants inhibited hypocotyl and radicle growth by 30.9
57.4% and 44.1
75.3%, respectively. Inhibitory active compounds may have been released from the plants into the sandwich method medium and inhibited the growth of the lettuce seedlings. The present results suggest that C. nardus and P. retrofractum are possible candidates for developing alternative natural herbicides in sustainable agriculture because of their strong inhibitory activity. Keywords : allelochemicals, natural herbicides, sustainable agriculture

have important medicinal properties, but rarely study in INTRODUCTION allelopathic activity. The present study, therefore, aimed to evaluate the allelopathic activity of 14 Thai medicinal Allelopathy is a phenomenon of chemical interactions plants on the seedling growth of lettuce for the purpose of among plants, and allelochemicals are chemicals released developing natural herbicides in the future. from one plant into the environment via volatilization, root exudation, leachates, and plant decomposition. The MATERIALS AND METHODS allelochemicals influence the germination and growth of neighboring plants in either an inhibitory or stimulatory Plant materials manner (Rice, 1984). In recent years, allelochemicals have Fourteen medicinal plants were collected from Chiang been studied and tested as bioherbicides for weed control. Mai, in northern Thailand: Andrographis paniculata Medicinal plants have been widely studied in the search for (Burm. f.) Wall. ex Nees, Cananga odorata (Lam.) Hook.f. potential natural active compounds (Batish et al., 2007; & Thomson, Cymbopogon nardus (L.) Rendle, Gomphrena Gilani et al., 2010). The allelopathic activity of 239 me- globosa L., Houttuynia cordata Thunb., Kaempferia dicinal plants was evaluated and 223 were found to have parviflora Wall. ex Baker, Michelia alba (DC.) Figlar, allelopathic activities (Fujii et al., 2003). The allelopathic Momordica charantia L., Ocimum tenuiflorum L., activity of numerous medicinal plants has also been re- Orthosiphon aristatus (Blume) Miq., Piper retrofractum ported (Syed et al., 2014; Synowiec and Nowicka-Po
e, Vahl, Combretum indicum (L.) DeFilipps, Ruellia tuberosa 2016). L., and Acmella oleracea (L.) R. K. Jansen. The whole Thailand is located in Southeast Asia and has a tropi- plants were washed under running tap water, dried in a cal climate, resulting in a wide diversity of plant species. greenhouse, and ground into a powder. Lettuce (Lactuca About 80% of at least 10,000 forest tree and herbal plant sativa var. Grand Rapids) was used as a test plant species species in Thailand are recognized for their medicinal prop- to determine biological activity. erties (Thitiprasert et al., 2007). Many of the species domi- Biological activity nate and form colonies with few or no other plant species Biological activity was determined using a modified around them. Their strong ability to garner natural re- sandwich method based on the method of Fujii et al. sources such as nutrients and water may allow them to es- (2003). The powder (50 mg) of each plant sample was tablish colonies. Their allelopathic ability may also be added to Petri dishes (5 cm). Agar (1.5%, 5 mL) was then involved in establishing colonies. The selected 14 Thai poured into the Petri dishes and mixed with the powder. medicinal plants in this study are common plants in north- After the agar gelatinized, 5 mL of agar was poured onto ern Thailand and grow as colonies in nature. All of them the surface of the gelatinized agar. The Petri dishes were

Corresponding author : Hisashi Kato-Noguchi, fax: ＋81
87
891
3086, e-mail : [email protected]

Vol. 55, No. 3 (2017) (
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 P. SUWITCHAYANON ET AL.

kept until the second layer of agar was gelatinized. Five hibited lettuce radicle growth by 75.3, 74.0, 71.9, and lettuce seeds were then arranged on the surface of the sec- 71.8%, respectively. ond layer of agar and incubated in the dark at 25°C for 48 These results indicate that the inhibitory effects of h. Controls were treated exactly as described above with- those medicinal plants were species dependent. All the me- out the plant powder. The length of the lettuce hypocotyls dicinal plants showed greater inhibitory effects on the let- and radicles was measured and the inhibition percentage tuce radicles than the hypocotyls. Because the radicles are was calculated by referring to the length of the control the first organ to emerge, they can absorb comopunds re- seedlings using the following formula: leased by the medicinal plants into the agar medium in the Petri dishes (Gniazdowska and Bogatek, 2005). Moreover, Treated hypocotyl K. parviflora (12), O. tenuiflorum (4), and M. alba (14) can or root length Inhibition (%)
1 100 cause radicle necrosis (visual symptoms are shown in Fig. Control hypocotyl   1). It has been reported that allelopathic compounds af- or root length fected physiological and biochemical processes of target Statistical analysis plants by changing membrane permeability which caused All experiments were conducted with 2 replicates (5 the over production of reactive oxygen species, resulting in seeds/replicate) and repeated twice (n＝20). The data on the degradation of lipids or lipid peroxidation and cell in- seedling growth were analyzed by SPSS version 16.0 using jury leading to necrosis symptom (Rice, 1984; Macías et one-way ANOVA and subsequent Tukey’s HSD tests at P al., 2004). The necrosis symptom occurred in this study ＜0.05. suggests that active compounds in each medicinal plant (12, 4 and 14) may affect some processes in cell membrane RESULTS AND DISCUSSION of lettuce radicals, and the radicals turn into brown and death at last. The inhibitory activities of the 14 medicinal plants on The combination of water extracts of some the growth of the lettuce seedlings are shown in Fig. 1. All allelopathic plants with a reduced dose of herbicides lead to the medicinal plants inhibited the hypocotyl and radicle an increase in weed control and yield improvement under growth of the lettuce seedlings (Table 1). At a concentra- field conditions (Ihsan et al., 2015; Khan et al., 2016). A tion of 50 mg dry plant weight, Cymbopogon nardus (1), mixed cultivation or intercropping of allelopathic plants commonly used as an insect repellent, showed the strongest under field conditions has also been reported to reduce inhibition, completely inhibiting both the hypocotyl and weed density and increase crop yield (Kathiresan, 2007; radicle growth of the lettuce. A few studies have reported that Cymbopogon species and their major constituents act Table 1 Effect of 14 medicinal plants on hypocotyl and radicle as allelopathic species in inhibiting the germination and growth of lettuce seedlings. seedling growth of test plants (Sousa et al., 2010; Alves et Inhibition (%) al., 2014). Treatment Radical Hypocotyl Piper retrofractum (2), a spice and seasoning, com- 1. Cymbopogon nardus 100.0 a 100.0 a pletely inhibited the hypocotyl growth and 93.5% of the 2. Piper retrofractum 93.5 a 100.0 a radicle growth of the lettuce seedlings. The plants in this 3. Orthosiphon aristatus 75.3 b 45.4 bcdef genus, such as P. sarmentosum, P. methysticum,andP. 4. Ocimum tenuiflorum 74.0 b 31.8 ef nigrum, have been reported to inhibit the growth of noxious 5. Momordica charantia 71.9 b 41.4 cdef weeds (Hong et al., 2002; Yan et al., 2006; Pukclai and 6. Acmella oleracea 71.8 b 47.4 bcd 7. Houttuynia cordata 69.9 b 45.4 bcdef Kato-Noguchi, 2011). 8. Ruellia tuberosa 65.9 bc 31.8 ef Kaempferia parviflora (12), Combretum indicum (13), 9. Gomphrena globosa 58.4 cd 30.9 f and Cananga odorata (11) inhibited lettuce hypocotyl 10. Andrographis paniculata 55.3 d 34.2 def growth by 57.4, 56.4, and 51.8%, respectively. In general, 11. Cananga odorata 52.4 de 51.8 bc 12. Kaempferia parviflora 51.6 de 57.4 b those plants are commonly used as herbal medicine for 13. Combretum indicum 44.1 e 56.4 bc multiple medicinal purposes, and perfume extraction. 14. Michelia alba 40.9 f 56.4 bc

However, the allelopathic activity of those plants has not LSD0.05 10.58 15.74 yet been reported. Orthosiphon aristatus (3), Ocimum Different letters show significant difference (P＜0.05) according tenuiflorum (4), M. charantia (5), and A. oleracea (6) in- to Tukey’s HSD test.

Fig. 1 Effect of 14 medicinal plants on lettuce seedlings after incubation for 48 h in the dark at 25°C.

(
) Environ. Control Biol. ALLELOPATHY OF MEDICINAL PLANTS

Abbasdokht et al., 2016; Yisa et al., 2016). This study sug- 2:143
147. gests that all 14 of the medicinal plants tested, especially C. Ihsan, M. Z., Khaliq, A., Mahmood, A., Naeem, M., El-Nakhlawy, nardus (1) and P. retrofractum (2), have possibility to F., Alghabari, F. 2015. Field evaluation of allelopathic apply their water extracts to reduce weeds in field condi- plant extracts alongside herbicides on weed management indi- ces and weed-crop regression analysis in maize. Weed Biol. tions for developing sustainable agriculture. Manage. 15:78
86. Kathiresan, R. M. 2007. Integration of elements of a farming CONCLUSION system for sustainable weed and pest management in the trop- ics. Crop Prot. 26: 424
429. This present research indicates that 14 medicinal Khan, M. A., Afridi, R. A., Hashim, S., Khattak, A. M., Ahmad, Z., plants collected from northern Thailand exhibited inhibi- Wahid, F., Chauhan, B. S. 2016. Integrated effect of tory activities on the growth of lettuce seedlings. The in- allelochemicals and herbicides on weed suppression and soil Triticum aestivum hibitory effects suggest that the medicinal plants may have microbial activity in wheat ( L.). Crop Prot. 90:34
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