Antibacterial agents from Dracaena cochinchinensis (Lour.) S.C.Chen and Eleutherine americana (Aubl.) Merr. Ex K. Heyne

Abstract

Fifteen compounds including two new anthraquinones (118-119), two naturally occurring new compounds (116-117) and eleven known compounds were successfully isolated from the CH2Cl2 extracts of Dracaena cochinchinensis and Eleutherine americana i.e. dihydrochalcones (5 and 23), pterostilbene (27), homoisoflavanones (15 and 82-84), naphthalenes (85 and 116), pyranonaphthoquinone (86) and anthraquinones (99-100 and 117-119). Among isolated compounds, (+)-eleutherin (86) was the most potent antibacterial agent against Propionibacterium acnes KCCM 41747, Staphylococcus aureus ATCC 25923, Streptococcus sobrinus KCCM 11898, Streptococcus mutans ATCC 25175 and Salmonella typhi ATCC 422 with inhibition zones of 14.7 to 18.0 mm and MIC values of 0.24 to 7.8 µM. Compound 86 showed bacteriostatic effect against P. acnes while bactericidal agent was observed by this compound against other tested bacteria. The combination of chloramphenicol and 86 demonstrated synergistic effect against all tested bacteria. Moreover, anti-allergic activity of nine compounds on the release of β-hexosaminidase in rat basophil leukemia (RBL-2H3) cells by calcium ionophore A23178-induced stimulation were investigated. Loureirin B (5) showed the strongest activity followed by 23 and 27 with IC50 values of 7.8, 15.8 and 17.5 µM, respectively. For anticancer activity, 86 suppressed the growth of HeLa, HCT116 and HepG2 cancer cell lines with IC50 values of 0.3, 4.6 and 6.7 µM, respectively. Compound 86 displayed twice more toxic than positive control (5-fluorourasil) against HeLa cells. The suppression against the cell was also shown by 23 and 27 with IC50 value of 1.4 µM.