Phytochemical, bioactivity and chemotaxonomy studies of dipterocarpus verrucosus foxw. ex sloot, dipterocarpus cornutus dyer and dipterocarpus crinitus dyer / Wan Zuraida Wan Mohd Zain

Dipterocarpus or commonly known as ‘keruing’ is an important source of dammarane, which contributes to a highly valued economic plant in Southeast Asia. Preliminary study revealed that this plant is rich in phenolic compounds and potential antioxidants. Thus, the stem bark of three Dipterocarpus species (D.verrucosus, D.cornutus and D. crinitus) are subjected to extensive chemical and biological studies. The sample was collected from UiTM Pahang Forest Reserve and was extracted in methanol and acetone via cold extraction method. Isolation was done using multiple techniques of chromatography and the structural elucidation of the compounds were characterized using spectroscopic techniques as well as comparison with literature. Phytochemical investigations successfully afforded 21 compounds with one compounds proposed as a new: 4’-O-methylepigallocatechin-3-O-(3”-O-methyl)gallate, two flavonoid: 4’-O-methylgallocatechin and 4’-O-methylepigallocatechin, fourteen oligomer resveratrol: (+)ampelopsin F, ampelopsin E, davidiol A, stenophyllol B, resveratrol, isohopeaphenol,(-)-ε- viniferin, (-)-ampelopsin A, laevifonol, (-)-α-viniferin, vaticanol B, hopeaphenol, hemslyenol D and diptoindonesin E, two terpene: β-sitosterol and β-sitosterol-glucoside and two coumarin: bergenin and scopoletin. Seventeen phytochemicals of sufficient quantities including three crude extracts were further tested for their antifungal activity. The activity comprising on Minimum Inhibitory Concentrations (MIC), Minimum Fungicidal Concentration (MFC) and germination assay against pathogenic strains namely Aspergillus flavus, A.oligosporus, Rhizophus oryzae and Fusarium oxysporum and F. oxysporum was found as the most sensitive. Resveratrol, ε-viniferin, ampelopsin F, cathecin, bergenin, and β-sitosterol glucoside at 0.1% inhibited more than 50% and were higher than the amphotericin B. MICs of D. verrucosus, D. cornutusand ε-viniferin against F. oxysporum were 3.8 μg/mL and were lower in comparison with amphotericin B (4 μg/mL). Germination assay revealed all samples possessed complete sterility (0%) at concentration 1, 2 and 4×MIC except for catechin, scopoletin, bergenin, α-viniferin, davidiol A and diptoindonesin E. Due to insufficient quantities, fourteen compounds were tested with 1,1-Diphenyl-2-picrylhydrazyl(DPPH) methods, while Total Phenolic Content (TPC), Ferric Thiocyanate (FTC) and Thiobarbituric Acid (TBA) were evaluated on three compounds only. Screening on antioxidant indicated all extract showed highest percent inhibition in all methods used FTC and TBA, DPPH while resveratrol, diptoindonesin E, catechin, ampelopsin A and scopoletin possessed IC50 between 100-1000 μg/mL. Structure analysis relationship revealed the presence of double bond of olefinic unit contributed to give high activity of both activities. Chemotaxonomy significance suggested close relationship between Dipterocarpus and Vatica which is classified under Dipterocarpeae tribe.