Two new flavonoids from the leaves of Garcinia smeathmannii, in vitro and in silico anti-inflammatory potentials

Garcinia smeathmannii is a well-known plant for its uses in the effective treatment of intestinal parasites, skin eruptions and skin burns. The dichloromethane-methanol (2:3) crude extract of the leaves of G. smeathmannii led to the isolation and characterization of twenty compounds (1-20) using chromatographic and spectroscopic techniques. Extracts and compounds were screened in vitro for their anti-inflammatory (ROS), antiglycation and antileishmanial (L. tropica) activities. Compounds were also screened for their in silico anti-inflammatory activities using Maestro 4.2.1 software with the co-crystal complex structures of the ovine oCOX-1: meloxicam (PDB Id: 4O1Z) and murine mCOX-2: meloxicam (PDB Id: 4M11) proteins. An unprecedented flavonol (1) and a flavone dimer (2) together with eighteen known compounds (3-20) were characterized. All the tested samples in vitro revealed no antiglycation and antileishmanial activities. Beside, extracts revealed moderate anti-inflammatory activities (IC₅₀ ranging from 24.1 ± 2.0 to 34.7 ± 0.8 μg/mL). Only compound (13) revealed an anti-inflammatory activity which was 9.33 times more active than the reference (Ibuprofen, IC₅₀ = 11.2 ± 1.9 μg/mL) with IC₅₀ of 1.2 ± 0.0 μg/mL. Compounds (2-9, 11-13 and 19-20) were docked and the docking scores were ranging from -10.178 to -6.119 (kcal/mol) which were in agreement with the experimental anti-inflammatory activity. These results are in agreement with the traditional uses of the leave of G. smeathmannii as cataplasm for skin eruption and as analgesic agent.