Methyl quadrangularates A-D and related triterpenes from Combretum quadrangulare

From the MeOH extract of leaves of Combretum quadrangulare, fifteen new cyc loartane-type triterpenes, methyl quadrangularates A-D (13) and N-P (8, 6, 12), methyl 24-epiquadrangularate C (5), quadrangularic acid E (9), 23-deox ojessic acid (10), 1-O-acetyl-23-deoxojessic acid (11), quadragularols A (7 ) and B (13) and norquadrangularic acids B (13) and C (15) were isolated to gether with two known cycloartane-type triterpenes, methyl 23-deoxojessate (16) and 4 beta,14 alpha-dimethyl-5 alpha-ergosta-9 beta,19-cyclo-en-3 beta -hydroxy-4 alpha-carboxylic acid (17). Betulinic acid (18), beta-sitosterol (19), kamatakenin (20), isokaempferide (21), 5,7,4'-trihydroxy-3,3'-dimeth oxyflavone (22) and 5,4'-dihydroxy-3,7,3'-trimethoxyflavone (23) were also obtained from the same extract. The structures of the new compounds were el ucidated on the basis of spectral analysis and chemical conversions. All th e isolated compounds were tested for their cytotoxicity towards highly live r metastatic murine colon 26-L5 carcinoma cells, and the cycloartane-type t riterpenes showed various degrees of cytotoxicity, whereas all the flavonoi ds possessed strong cytotoxicity with ED50 values equal to or less than 6 m u M.