Anticancer activity of rhamnoallosan against DU-145 cells is kinetically complementary to coexisting polyphenolics in psidium guajava budding leaves

Psldlum guajava L. is a valuable farm fruit plant having many medicinal uses. Previously its budding leaves (PE) were shown to contain huge amounts of soluble polyphenols (SP) including (in mg/g) gallic acid (348), catechin (102), epicatechin (60), rutin (100), quercetin (102), and rutin (100) and to exhibit potent anticancer activity. However, reconstitution of these polyphenols recovered only 40% of the original bioactivity, and the soluble carbohydrate (SC) portion in PE was suspected to contribute the remaining. PE contained a novel rhamnoallosan, which had a carbohydrate/protein (w/w) ratio = 29.06%/10.27% (=2.83, average molecular mass of 5029 kDa), characteristically evidencing a peptidoglycan, consisting of a composition (mole % ratio) of rhamnose/allose/arabinose/tallose/ xylose/fucose/glucose/mannose/galactose = 36.05:24.24:8.76:7.95:7.37:5.90:3.69:3.19:2.85 and of amino acid (in wt %) glycine/leucine/proline/alanine/methionine/isoleucine/valine/histidine/tyrosine/ phenylalanine/cysteine/aspartic acid/lysine/glutamic acid=37.12:12.68:10.05:8. 97:5.99:4.89:4.83:4.25: 4.05:2.78:1.86:1.10:0.73:0.70. Kinetic analysis showed comparable apparent cell-killing rate coefficients (K _app) to be 4.03 x 10 ³ and 2.92 x 10 ³ cells mg ^-1 h ^-1 respectively, by SP and SC, evidencing the complementary anti-DU-145 bioactivity in nature.