Phenolic Constituents from the Tree Barks of Garcinia cf cymosa and their Antioxidant and Antibacterial Activities

Two isoprenylated xanthones, α-mangostin (1) and β-mangostin (2) were isolated from the tree barks of Garcinia cf cymosa, along with the flavanol epicatechin (3). Their structures were elucidated by analysis of spectroscopic data. Compounds 1-3 exhibited moderate in vitro antibacterial activity against Staphylococcus aureus and Bacillus sp, while in the 1,2-diphenyl-picryl-hydrazyl (DPPH) antioxidant assay system only compound 3 showed moderate free radical scavenging activity, with IC50 value of 41.8 ppm. | Antibacterial | antioxidant | flavanol | Garcinia cf cymosa | xanthones | ® 2013 Ibnu Sina Institute. All rights reserved. http://dx.doi.org/10.11113/mjfas.v9n3.94


INTRODUCTION
The genus Garcinia (Clusiaceae or Guttiferae) comprises about 200 species and occurs in moist tropical regions, including Southeast Asia [1,2].Phytochemical investigations have shown that this group of plants, such as Garcinia mangostana, are very rich inphenolic compound, prenylated xanthones and flavonoids [3,4].Biological studies on the constituents of the fruits of G. mangostana demonstrated antibacterial, antifungal, antitumor promotion, and other biological activities [3,5,6].The present work on the tree barks of Garcinia cf cymosa collected from Muarobungo District, Jambi Province, Sumatra, Indonesia was investigated for the first time to evaluate the phytochemical profil of this endemic plant in comparison with that of other related species.This preliminary investigation led to the isolation of two prenylated xanthones, namely, α-mangostin (1) [7][8][9] and β-mangostin (2) [10,11] along with a flavanol epicatechin (3) [4].The structural characterization, as well as antioxidant and antibacterial evaluation of these compounds against Escherichia coli, Staphylococcus aureus and Bacillus sp, are discussed herein.

EXPERIMENTAL SECTION
General Experimental Procedures.Melting points were determined using a Fisher Jhone micromelting point apparatus and are uncorrected.Ultraviolet (UV) spectra were recorded on a UV-Vis spectrophotometer 1700 Series in MeOH and infrared (IR) spectra on a Perkin Elmer 1600 Series.spectrophotometer in CHCl 3 .The 1 H and 13 C NMR, COSY, HMQC, and HMBC were run on JEOL JNM-ECS 400 spectrometers.All mass spectra were taken under high resolution time of flight mass spectrum (HRTOFMS) conditions with Waters PremierXE spectrometer.Thin layer chromatography (TLC) was done on GF 254 (Merck).
Plant Material.Garcinia cf cymosa was collected in Juni 2011 from the region of Muarobungo District, Jambi Province, Indonesia, and authenticated by the Herbarium Bogoriensis, Indonesian Institute of Sciences, Cibinong, Bogor, Indonesia.A voucher speciment has been deposited at the Herbarium.
Extraction and Separation.The air-dried powdered tree barks of Garcinia cf cymosa (5 kg) were exhaustively macerated with MeOH at room temperature, and concentrated to give a dark brown crude extract (647 g).Part of the MeOH extract (200 g) was successively fractionated by column chromatography on silica gel and eluted with a gradient of n-hexane and dichloromethane, and then ethyl acetate to obtain 15.2, 21.4, and 38.7 g of the respective residues after evaporating the solvents.
Antibacterial Activity.The isolated compounds, α-mangostin (1), β-mangostin (2), and epicatechin (3) were evaluated for their antimicrobial activities against Escherichia coli, Staphylococcus aureus, and Bacillus sp. using disk-diffusion method.Zone of inhibition was determined after incubation at 37 o C for 48 h.Zone diameter of each compounds against E. coli, S. aureus, and Bacillus sp. are tabulated in Table 4.The data indicated that α-mangostin (1), showed high antibacterial activity against S. aureus and Bacillus sp. by producing zone of inhibitions of 3.4 and 3.2 mm, respectively, greater than that of chloramphenicol as a standard, with a zone of inhibitions of 2.6 -2.7 mm.However, α-mangostin (1) showed very low activity against E. coli compared to standard.β-Mangostin (2) also showed similar tendency, but with higher antibacterial effects with 6.3 and 5.0 mm of zone inhibiition, respectively against S. aureus and Bacillus sp.On the other hand, compound 3 showed only antibacterial activity against Bacillus sp.Antioxidant activity.DPPH radical scavenging assay was used to evaluate the antioxtdant activity of the isolated compoumds 1-3, and the results were compared with that of ascorbic acid as a standard.The data obtained (see Table 5).Indicated that α-mangostin (1) and β-mangostin (2) shown no antioxidant activity with, IC 50 566,6 and 250,5 ppm, respectively, while epicatechin (3) is moderately active, with IC 50 41.8ppm.These results indicated that the phenolic constituents obtained from polar fraction was responsible for the antioxidant phenomena.3).

α-Mangostin
Antibacterial and Antioxidant Activities.The isolated compounds, α-mangostin (1), β-mangostin (2), and epicatechin (3) were evaluated for their antimicrobial activities against Escherichia coli, Staphylococcus aureus, and Bacillus sp. using disk-diffusion method.Zone of inhibition was determined after incubation at 37 o C for 48 hr and compared to that of chloramphenicol as the standard.For zone diameters of each isolated compounds 1-3 against E. coli, S. aureus, and Bacillus sp.(see Table 4).DPPH radical scavenging assay were used to evaluate the scavenging ability of radicals in vitro by solutions of compoumds 1-3 (50 µM) in MeOH (450 ml) and the final absorbance was recorded on microplate reader at 516 nm.The results were tabulated and compared with that of ascorbic acid as a standard (see Table 5).