29-8 |
|
C. K. M. LAI, The Department of Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China and P. C. K. Cheung, Food and Nutritional Sciences Programme, The Chinese University of Hong Kong, Shatin, New Territories, HongKong, China. Mushroom sclerotia which are a dry solid mass of fungal hyphae, have been used as a traditional Chinese medicine. Previous studies have shown that alkali-soluble polysaccharides of two kinds of mushroom sclerotia, Pleurotus tuber-regium and Poria cocos, being b-(1®3)-glucans can mediate the immunological responses of the hosts by exerting antitumor and/or cytotoxic effect. The objective of this project is to isolate different sclerotial polysaccharides for their chemical characterization and evaluation of antitumor activity. Polysaccharides were isolated from five scleortia, namely Pleurotus tuber-regium, Polyporus rhinoceros, Poria cocos, Polyporus umbellatus and Polyporus mylittae into different fractions by sonication in alkaline medium, hot water and alkali extractions. Chemical characterization of the monosaccharide composition and molecular weight of the polysaccharides were determined by using GC and HPLC, respectively. In vitro assays using human acute leukemia cell (HL-60) and normal monkey kidney cell (VERO) were used to evaluate the antitumor activity and cytotoxicity of the isolated fractions at 50, 100, 200 mg/ml levels by MTT assay. Our results showed that sonication in an alkaline medium followed by lyophilization gave a remarkable yield (>60%) of crude polysaccharides in P. rhinoceros, P. cocos and P. mylittae. Results from GC revealed that all extracts contained about 90% of glucose, while those from HPLC showed that their molecular weight were larger than 800,000. In vitro antitumor experiments showed that fractions from sonication, hot water and alkali extraction of P. umbellatus and hot water extracts of P. mylittae had antiproliferative effects of HL-60 of ³40% (p <0.05). No fractions inhibited the growth of Vero cells. The side effects brought about by the existing anticancer drugs would be greatly alleviated by the use of Biological Response Modifiers (BRMs) such as mushroom polysaccharides. Hence, the antitumor effects of these sclerotial polysaccharides could be explored as an alternative cancer treatment.
Session 29, Food Chemistry: Antioxidants and bioactive agents
|