Secondary metabolites from the barks of Garcinia griffithii T. anderson (Clusiaceae) and their chemophenetic significance

A total of thirteen compounds consisting of nine xanthones; cowagarcinone C (1), doitunggarcinone C (2), nigrolineaxanthone E (3), nigrolineaxanthone Q (4), β-mangostin (5), 7-O-methylgarcinone E (6), dulcisxanthone F (7), ananixanthone (8) and nigrolineaxanthone N (9), two polycyclic polyprenylated acylphloroglucinols (PPAPs); garcinielliptone J (13) and garcinialone (14) as well as two terpenoids; 30-hydroxycycloartenol (15) and garcinane (16), were putatively identified with a good confidence level from dichloromethane extract of Garcinia griffithii T. Anderson using the ¹³C NMR-based dereplication and MixONat software. In addition, three xanthones; euxanthone (1,7-dihydroxyxanthone) (10), forbexanthone (11) and 1,5-hydroxy-3,6-dimethoxy-2,7-diprenylxanthone (12) were successfully isolated. The structure of the isolated compounds was confirmed through the analysis of spectroscopic data and comparison with reported data. The ¹³C NMR data of forbexanthone (11) was reported for the first time. Interestingly, the dichloromethane extract and 1,5-dihydroxy-3,6-dimethoxy-2,7-diprenylxanthone (12) which were evaluated for their exhibited α-glucosidase inhibitory activity exhibited potent inhibition toward the enzyme with IC₅₀ values of 0.66 μg/mL and 3.02 μM, respectively as compared to the standard, acarbose (IC₅₀ = 392 μg/mL or 608 μM). Notably, ananixanthone (8) has not been reported from the genus Garcinia while compounds 1–7, 9, 11 and 13–16 being reported from Garcinia griffithii for the first time. In addition, the chemophenetic significance of all the compounds has also been discussed.