Previous phytochemical investigations reported that Calophyllum spp have biosynthesized a wide range of bioactive phenolics such as xanthones and coumarins. The phytochemical study conducted on the stem bark of C. canum has led to the isolation of eight trioxygenated xanthones namely: 5-methoxytrapezifolixanthone (1), 5-methoxyananixanthone (2), caloxanthone C (3), 1,5-dihydroxy-3-methoxy-4-isoprenylxanthone (4), 6-deoxyisojacareubin (5), euxanthone (6), trapezifolixanthone (7), ananixanthone (8), together with three common triterpenoids, β-sitosterol (9), friedelin (10), and stigmasterol (11). Furthermore, xanthones 1 and 2 were isolated for the first time as naturally occurring xanthones from the plant extract. The structures of these compounds were identified and elucidated using advanced spectroscopic techniques such as 1 D & 2 D NMR, MS, and FTIR. The neuroprotective property of selected compounds was tested through in vitro stroke model. Among all tested compounds, 1 µm of compounds 8, 9, and 10 showed significant neuroprotective activity via reduction of apoptosis by ∼ 50%.
The title compound (trivial name brasixanthone B), C23H22O5, isolated from Calophyllum gracilentum, is characterized by a xanthone skeleton of three fused six-membered rings plus an additional fused pyrano ring and one 3-methyl-but-2-enyl side chain. The core xanthone moiety is almost planar, with a maximum deviation 0.057 (4) Å from the mean plane. In the mol-ecule, an intra-molecular O-H⋯O hydrogen bond forms an S(6) ring motif. The crystal structure features inter-molecular O-H⋯O and C-H⋯O inter-actions.
In search for new metabolites from the stem bark of Calophyllum soulattri and Calophyllum gracilentum, led to the isolation of a new xanthone, soulaxanthone (1), along with four other known metabolites, euxanthone (2), calopolyanolide E (3), calanolide E (4) and friedelin (5). The structures of these compounds were identified and elucidated using spectroscopic techniques such as 1H NMR,13C NMR, COSY, DEPT, HSQC, HMBC, MS and FTIR. The antibacterial activities of compounds 1-5, as well as the extracts, were tested against five bacterial strains. Soulaxanthone (1) exhibited moderate activity against Pseudomonas aeruginosa with an MIC value of 25 µg/mL. Hexane (non-polar) extract from both plants exhibited moderate activity against Enterobacter cloacae (MIC = 250 µg/mL). Calopolyanolide E (3) and friedelin (5) showed bactericidal activity against Enterobacter cloacae (MBC = 50 µg/mL), thus the compounds have the potential to serve as a new lead for developing effective antibacterial medication.