Australian Journal of Basic and Applied Sciences, 6(8): 431-436, 2012 ISSN 1991-8178

Antioxidant, Antimicrobial and Cytotoxic Activities of Resveratrol Oligomers of Shorea macroptera Dyer

1Nur Ainaa Atikah Mohd Nazri, 1Norizan Ahmat, 1Mashita Abdullah, 1Norrizah Jaafar Sidik, 2Syed Ahmad Tajudin Tuan Johari

1Faculty of Applied Sciences, Universiti Teknologi MARA, , 40450 Shah Alam, Selangor, Malaysia 2Faculty of Agriculture and Biotechnology, Universiti Sultan Zainal Abidin,20400 Kuala Terengganu, Terengganu, Malaysia

Abstract: Eight resveratrol oligomers were isolated from the acetone extract of the stem bark of Shorea macroptera by using various chromatographic techniques. The structures were determined based on spectroscopic data including UV, IR, 1D and 2D NMR. The data were compared with related data reported previously. The similarity to the published data suggested that the compounds were ε- viniferin (1), laevifonol (2), both are dimer resveratrols, davidiol A (3), stenophyllol B (4), trimer resveratrols and four tetramers which are hemsleyanol D (5), hopeaphenol A (6), hopeaphenol (7) isohopeaphenol (8). These compounds were evaluated for their free radical scavenging, antimicrobial and cytotoxic activities. Among these compounds, compound 5 displayed significant free radical scavenging activity with IC50 63.2µg/ml, compound 3 inhibited the growth of S. uberis and B. subtilis at 20 µg/ml per disc while compounds 1 and 3 displayed significant cytotoxic activity against HL-60 and HeLa cell lines.

Key words: , Shorea macroptera, oligomer resveratrol, free radical scavenging, antimicrobial, cytotoxicity

INTRODUCTION

The Malaysian tropical forest is home to a large number of and is considered to be one of the richest in the world. It is estimated that there are about 1,230 plants species with medicinal value in the peninsular of Malaysia. Dipterocarpaceae is a large family of tropical plants, consisting of Anisoptera, Cotylelobium, , Dryobalanops, Hopea, Neobalanocarpus, Parashorea, Shorea, Stemonoporus, Upuna, Vateria, Vateriopsis and Vatica, with about 600 species (Ashton, 1982). Shorea is the main genus in the Dipterocarpaceae family which has about 150 species. The resin of Shorea is used in indigenous medicine as an astringent, and also used to treat diarrhea and dysentery (Shiva and Jantan, 1998). It also used as an ingredient of ointment for skin diseases, ear troubles, toothaches, sore eyes, ulcers and wounds. Seed of Shorea species especially which is under Red Meranti group, produces illipe nuts which are called engkabang or tengkawang in Malaysia and Indonesia. The illipe fat extracted from the kernel is used in confectionary industry especially in the manufacture of chocolates. Likewise, the illipe fat can also be added to cosmetic such as lipstick (Shiva and Jantan, 1998). The wood of Shorea is used for planks, temporary construction, packing cases, and furniture (Heyne, 1987). Processing of wood produced a lot of waste wood which can be used for medical or cosmetic agent as well and some of them have been used as traditional medicine. Research on chemical constituents in Dipterocarpaceae has been going on for many years. This family produces a wide variety of terpenoids, flavonoids, arylpropanoids and oligomer resveratrol. Based on previous study, plants from Dipterocarpaceae family especially from genus Shorea possess bioactive resveratrol oligomers such as rat liver 5α-reductase inhibitor (Hirano et al., 2001), cytotoxic (Wibowo et al., 2011), antibacterial (Zain and Ahmat, 2011) and anti-tyrosinase activity (Ohguchi et al., 2003). In continuation for the search of bioactive plants of Malaysia (Mohd Nazri et al., 2011; Norizan et al., 2012) and oligomer resveratrols (Nazri and Ahmat, 2011; Norizan et al., 2011; Wibowo et al., 2011; Zain et al., 2011; Zawawi et al., 2011) we describe here the free radical scavenging, antimicrobial and cytotoxic activities of compounds isolated from Shorea macroptera.

Experimental Section: General Procedures: The 1H-NMR and 13C-NMR were recorded in acetone-D on Bruker 300 Ultrashield NMR spectrometer measured at 300 and 75 MH. Chemical shifts are reported in ppm and the coupling constants are given in Hz. Melting point was taken on a hot stage Gallen Kamp melting point apparatus with microscope and was

Corresponding Author: Norizan Ahmat, Faculty of Applied Sciences, Universiti Teknologi MARA, Malaysia, 40450 Shah Alam, Selangor, Malaysia Tel: +603-55444643, Fax: +603-55444562. E-mail: [email protected] 431

Aust. J. Basic & Appl. Sci., 6(8): 431-436, 2012 uncorrected. The infrared (IR) was recorded on the Perkin Elmer spectrum one FT-IR spectrometer. The ultraviolet spectra were recorded on Shimadzu UV-Vis 160i. Vacuum liquid chromatography (VLC) used silica gel 60, 70-230 mesh ASTM (Merck 1.07747), radial chromatography used Si-gel 60 PF (Merck catalog 254 number: 1.07749). Aluminium supported silica gel 60 F254 was used for thin layer chromatography.

Plant Material: The bark of Shorea macroptera Dyer (6 kg) was collected from Balok Forest Reserve, Pahang, Malaysia. The sample was identified by the botanist from the Institute of Bioscience, Universiti Putra Malaysia, Malaysia and Universiti Teknologi MARA, Malaysia.

Extraction and Isolation: The dried bark of Shorea macroptera Dyer (6 kg) was ground and macerated with acetone for 72 hours. The acetone extract was concentrated using rotary vacuum evaporator. The crude extract (300 g) was partitioned using diethyl ether and concentrated to afford diethyl ether crude extract. The diethyl ether crude extract (115 g) was subjected to vacuum liquid chromatography (VLC) using gradient elution system of Hex: Ea and seven fractions were obtained. Fraction 2 was purified by second VLC (Hex-Ea system), radial chromatography repeatedly (Hex:CHCl3:MeOH system) to yield compound 1 (10mg). Compound 2 (100 mg) was obtained from fraction 6 by repeated VLC (CHCl3: Acetone) and radial chromatography (CHCl3:MeOH). Fraction 4 (8 g) was subjected to VLC (CHCl3: Acetone) and purified repeatedly using radial chromatography (CHCl3:MeOH system) to give compound 3 (135 mg). Fraction 5 (33.9 g) was subjected to VLC (Hex: Ea: Ac system) and purified by radial chromatography repeatedly (CHCl3:MeOH system) to give compound 4 (15 mg), 5 (25.4 mg), 6 (10 mg), 7 and 8 (50 mg).

DPPH Radical Scavenging Activity: The antioxidant activity of the extracts and pure compounds were evaluated with radical scavenging activity of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals according to the previous procedure described by (Noridayu et al., 2011). Stock solutions of extracts and pure compounds were prepared at 1000 ppm in methanol. The stock solutions were diluted to different concentrations (500 ppm to 7.8125 ppm in methanol) in a 96-well microtiter plate. Then, 5 µl DPPH solutions (prepared as 5 mg DPPH in 2 ml methanol) were added to each well. The plate was shaken gently and placed in the dark for 30 minutes at room temperature. The absorbance was then measured at 517 nm using Elisa Reader. Percentage inhibition was calculated using the following formula: Absorbance (DPPH) – absorbance (DPPH + sample) × 100 Absorbance (DPPH)

The IC50 value of DPPH indicates the concentration needed to scavenge 50 % DPPH free radicals. All test analysis were run in triplicates and averaged. Butylated hydroxyanisole (BHA) serves as positive control, while methanol was used as negative control.

Disc Diffusion Method: Antimicrobial tests were carried out by the discs diffusion method using the suspension containing 108 CFU ml-1 bacteria or 107 CFU spread on Nutrient Agar (NA) respectively. The discs were impregnated with 20µL stock solutions of the extract (100, 50, 250 and 50 mg/ml) or pure compound (1, 0.5 and 0.25 mg/ml) placed on the inoculated agar. The inoculated plates were incubated for 24 hours at 37°C for bacteria strains. Streptomycin (25 µg/disc) served as positive control for the bacteria. Antimicrobial activities were evaluated by measuring the inhibition zone against the test organisms. The assays in these experiments were repeated in triplicate (Medine et al., 2004). The results recorded as very inhibitory (>20 mm), moderately inhibitory (10-19 mm), slightly inhibitory (6-9 mm) and non-inhibitory (0mm).

Cytotoxic assay: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl Tetrazolium Bromide (MTT) Assay: The cytotoxicity assay was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay (Khorshid et al., 2011). Cells were seeded in 96-well microplate at 3 x 105 cell/ml, incubated at 37°C in 5% CO2 and treated with sample at 2 x MFC in Serum Free Medium (SFM) for 240-480 min. The culture medium was aspirated, replaced with 0.5 µg/ml MTT solutions and incubated for 30 min in a CO2 incubator. The solution was aspirated and added with 1000 µl DMSO to dissolve the formazan crystals. After 30 min of rotary agitation, the absorbance of the solution was measured at 570 nm using Genesis 10 UV-Vis spectrophotometer (Thermo Spectronic, NY, USA). The viable cell number was calculated from the standard curve of cell number by plotting a scattergram of the absorbance value against the known number of cells. IC50 values represent the compound’s concentration that reduces the mean absorbance at 570 nm to 50% of those in the untreated control wells.

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RESULTS AND DISCUSSION

Eight oligomer resveratrols namely ε-viniferin (1), laevifonol (2); dimer resveratrols, davidiol A (3), stenophyllol B (4); trimer resveratrols and hemsleyanol D (5), hopeaphenol A (6), hopeaphenol (7) isohopeaphenol (8); tetramer resveratrols have been isolated from the stem-bark of Shorea macroptera and the molecular structures were illustrated in Figure 1. Seven compounds except 4 have been reported to occur in Shorea and also in Dipterocarpaceae family. Compound 4, however, was found in Vatica of Dipterocarpaceae (Atun et al., 2004; Ito et al., 2003).

Fig. 1: Molecular structure of compounds isolated from the stem-bark of Shorea macroptera.

Shorea macroptera extract (SME) and some of the isolated compounds have been tested for antioxidant, antibacterial and also cytotoxic activities. Synergetic effect can be seen where the SME showed good antioxidant and antibacterial activities compared to the isolated compounds. In DPPH radical scavenging

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Aust. J. Basic & Appl. Sci., 6(8): 431-436, 2012 activity (Figure 2 and Table 1), the SME showed good antioxidant activity followed by hopeaphenol (5) hopeaphenol A (6) with IC50 of 59.1, 63.2 and 252.0 µg/ml respectively. Our previous study on antioxidant and antibacterial activities of several Shorea species showed SME as good radical scavenger and good antioxidant potential based on DPPH and ferric thiocyanate (FTC) analysis (Norizan et al., 2012). SME was reported as excellent scavenger which is better than that of the control, butylhydroxytoluene (BHT) and the percent inhibition is better than vitamin E in FTC analysis.

Figure 2: Radical Scavenging activity of Shorea macroptera extract and its isolated compounds.

Table 1: IC50 (µg/ml) for free radical scavenging activity of Shorea macroptera extract and its major isolated compound. Compound IC50 (µg/ml) Shorea macroptera extract 59.1 Hopeaphenol (5) 63.2 Hopeaphenol A (6) 252.0 Stepnophyllol B (8) 440.2

In antibacterial test, SME was found to show selective inhibition against bacteria as shown in Table 2. It inhibited moderately the Gram positive bacteria of skin and oral pathogen microbes such as S. aureus, B. subtilis, S. anginosus and S. uberis. At low concentration (250µg/disc), the SME was still able to inhibit weakly the growth of S. uberis. Antibacterial assay on the pure compounds showed that only compounds 3 and 4 displayed potent inhibitions against bacteria. Compound 3 shows moderate inhibition against S. uberis and B. subtilis at 20 µg/disc while compound 4 inhibited weakly S. aureus at 20 µg/disc. In the cytotoxic activity, ε-viniferin (1), laevifonol (2), davidiol A (3), stenophyllol B (4), and hemsleyanol D (5) were assayed against three cell lines namely HeLa (human cervical cancer), HL-60 (human promyelocytic leukemia), MCF-7 (human breast adenocarcinoma cancer) using MTT assay. Compound 1 and 3 displayed strong cytotoxic effects against HL-60 cell line which the IC50 IC50 9.0 and 9.1 µg/ml respectively. 1 inhibited moderately HeLa cell line (IC50 17.1 µg/ml while 4 inhibited weakly HeLa and HL-60 cell lines. However, all compounds were found to inhibit >30 µg/ml the growth of MCF-7. By comparing the activity of the resveratrol oligomers towards the three tests, compound 3 was found to show significant antibacterial and cytotoxic activity compared to that of other compounds. Zgoda-Pols et al (2002) reported that 6 and 7 displayed better antioxidant activity, while Yim et al., (2009) stated that compound 6 as active against methicillin-resistant Staphyllococcus aureus and Mycobacterium smegmatis. Besides, compound 1 which was found in Vitis amurensis, demonstrated antimicrobial activity against two oral pathogens, Streptococcus mutans and Streptococcus sanguis (Yim et al., 2009). Compound 2, an ascorbic acid derivative was not active towards all assays. This observation suggests that the ascorbic acid moiety to significantly decrease its therapeutic property.

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Table 2: Antibacterial activity of Shorea macroptera extract and six isolated compounds. Sample Dosage Microorganism (Inhibition zone: mm) (µg/disc) S. S. anginosus S. uberis B. subtilis S. thyphimurium P. E. coli aureus aeruginosa Shorea 1000 11 10 12 8 - - - macroptera 500 - - 11 9 - - - extract (SME) 250 - - 6 - - - - Positive 18 18 18 18 18 18 18 control 20 ------ε-viniferin (1) 10 ------5 ------Positive 18 18 18 18 18 18 18 control 20 ------Laevifonol (2) 10 ------5 ------Positive 18 18 18 18 18 18 18 control 20 - - 8 8 - - - Davidiol A 10 - - - 7 - - - (3) 5 ------Positive 14 14 14 14 14 14 18 control 20 6 ------Stenophyllol 10 ------B (4) 5 ------Positive 18 18 18 18 18 18 18 control Hemsleyanol 20 ------D (5) 10 ------5 ------Positive 18 18 18 18 18 18 18 control 20 ------Hopeaphenol 10 ------A (6) 5 ------Positive 18 18 18 18 18 18 18 control * positive control is streptomycin

Table 3: IC50 values (µg/ml) for cytotoxic activity of resveratrol oligomers from Shorea macroptera.. Compound Cell lines HeLa HL-60 MCF-7 ε-viniferin (1) 17.1 9.0 >30 Laevifonol (2) >30 >30 >30 Davidiol A (3) 20.0 9.1 >30 Stenophyllol B (4) 28.2 25.0 >30 Hemsleyanol D (5) >30 28.2 >30

IC50 activity (inhibition): very strong <5 μg/ml; strong >5–10 μg/ml; moderate: 10–20 μg/ml; weak: 20–100 μg/ml and not active >100 μg/ml (Wibowo et al., 2011)

Conclusion: In summary, phytochemical study of Shorea macroptera has led to the isolation of eight resveratrol oligomers namely ε-viniferin (1), laevifonol (2), davidiol A (3), stenophyllol B (4), hemsleyanol D (5), hopeaphenol A (6), hopeaphenol (7) and isohopeaphenol (8). Shorea macroptera extract itself showed good antioxidant and antibacterial activities compared to individual isolated compounds. Compound 3 may be considered as antibacterial and cytotoxic agents compared to the others, while compound 5 displayed significant free radical scavenging activity.

ACKNOWLEDGMENTS

The authors would like to thank the Faculty of Applied Sciences and Universiti Teknologi MARA Malaysia for financial support (DanaKep Grant: 600-RMI/ST/DANA 5/3/Fst 431/2011). One of the authors’ scholarship is financed by the National Science Fellowship (NSF), Ministry of Science, Technology and Innovation (MOSTI).

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