Chemical constituents and bioactivities of garcinia griffithii T. Anderson

Abstract

Chemical and bioactivity investigations were carried out on the leaves andstem barks of Garcinia griffithii T. Anderson from Guttiferae family. Sample foreach part of the plant was extracted consecutively with increasing polarity of solvents by Soxhlet method. Vacuum liquid chromatography and column chromatography were used to purify the crude extracts. The pure compounds were elucidated by using combined spectroscopic techniques which include UV, IR, NMR(1D and 2D) and MS. Chromatographic purification of the leaves extracts haveafforded nine pure compounds identified as squalene, 28-hydroxyfriedelan-3-one,friedooleanan-3-one, olean-12-en-3-ol, amento-4'-methyl ether, 3,8''-binaringenin,3,8''-binaringenin-7''-O-glucoside, morelloflavone and morelloflavone-7''-Oglucoside.Chromatographic purification of the ethyl acetate and methanol extracts of the stem barks yielded two compounds identified as amento-4'-methyl ether andmorell of lavone. The crude extracts and pure compounds isolated from methanolcrude extract of the leaves were screened for various types of antioxidant assay and tyrosinase inhibition activities. The antioxidant assay on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical showed that the crude n-hexane extract of the stembarks had the highest radical scavenging activity with IC50 = 96.43 ± 2.69 μg/mL,while morelloflavone was found to be the strongest antioxidant compound with IC50= 57.57 ± 0.53 μg/mL compared to other compounds. The crude methanol extract ofthe stem barks showed the highest total antioxidant with 260.81 ± 2.21 mg/g ofascorbic acid equivalent (AAE/L) and 871.43 ± 6.62 mg/g of butylated hydroxyltoluene equivalent (BHTE/L) while the crude methanol extract of the leaves showed the highest total phenolic content with 444.10 ± 6.67 mg/g of gallic acid equivalent(GAE/L) and 423.10 ± 6.67 mg/g of ( ± )-cathechin equivalent (CE/L).Morelloflavone showed the highest value for both assays with values 58.50 ± 3.15mg/g of AAE/L and 264.50 ± 9.45 mg/g of BHTE/L; and 841.33 ± 38.28 mg/g ofGAE/L and 822.97 ± 33.93 mg/g of CE/L, respectively. The crude extracts and all compounds were found to have weak anti-tyrosinase activity. The antimicrobialassay of all the crude extracts were carried out by using disc diffusion method,followed by minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC). The methanol crude extract of the leaves showed the most significant antimicrobial activity towards E. faecalis and K. pneumoniae with MIC and MBC value ranged between 225 – 450 μg/mL compared to the other crude extracts.