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Unripe apples, pears, and peaches were examined for their abilities to activate the complement system. Among the hot water extracts of unripe fruits, a peach extract (PP-0) showed the highest anti-complementary activity in a dose-dependent manner. Activity of PP-0 was resistant to digestion with pronase, but sharply decreased by NaIO_4 oxidation. These results indicate that complement activation by PP-0 is mainly due to polysaccharide moiety. PP-0 was fractionated by ethanol precipitation and cetavlon treatment to give subfractions, PP-2, PP-3, and PP-4. An acidic polysaccharide subfraction PP-2 showing highest activity was further purified by two successive column chromatographies on DEAE-Sepharose FF and Sepharose CL-6B, and resulted in a purified polysaccharide, PP-2-V-A. PP-2-V-A was eluted as a single Peak on HPLC, and its molecular mass was estimated as 218 kDa. PP-2V-A mainly contained neutral sugars (38%) such as arabinose (17%) and galactose (11%) with a considerable amount of galacturonic acid (61%). Results obtained by crossed immunoelectrophoresis using anti-human C3 and anti-complementaly activity in the absence of Ca^(++) ion suggested complement activation by PP-2-V-A from unripe peaches occurs via alternative and classical pathways.
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