Chemical examination of the methanolic extract of the leaflets of CYCAS CIRCINALIS L. led to the isolation of one new biflavonoid, (2 S, 2'' S)-2,3,2'',3''-tetrahydro-4',4'''-di- O-methylamentoflavone (tetrahydroisoginkgetin; 2), and 15 known compounds, 11 of which are reported for the first time