avonoid Derivatives from Lophira alata Stem Heartwood

The stem heartwood of Lophira alata Banks ex C. F. Gaertn. (Ochnaceae), also called “bongossi”, shows strong resistance against destructive fungi and bacteria and is extensively exploited as fi rst-grade timber. Both aqueous and alcohol extracts of either the leaves, the stem bark or the stem heartwood of this plant are extensively used as antiseptics by many tribes in the central and southern regions of Cameroon. The observed antimicrobial properties of the MeOH extract of its stem bark (Malcolm and Sofowora, 1969; Murakami et al., 1991) initiated its phytochemical investigation that led to the characterization of the antimicrobial bifl avonoids mbamichalcone (Tih et al., 1988) and bongosin (Tih et al., 1990), the tetrafl avonoids lophirachalcone, lophirafl avan A (Tih et al., 1992a), lophirafl avans B and C (Tih et al., 1992b), and the hexafl avonoid azobechalcone (Tih et al., 1999). Recently, investigation of the MeOH leaf extract gave luteolin, lithospermoside (Tih et al., 2003), and lophirones L and M (Tih et al., 2006). The women of the Bafi a and the Yambassa tribes living in the Ombessa district of the Mbam division in the centre region of Cameroon use the aqueous extract of the stem heartwood for gynaecological cleansing. In order to understand the antiseptic action of this extract, we have extended our phytochemical investigation to the stem heartwood methanol extract of this plant from which we have isolated and characterized, using spectroscopic and chemical evidences, six isofl avonoid derivatives of which three are new.