Abstract:

Opuntia milpa alta was used as raw material to extract active polysaccharaides by hot water extraction. Extracted Opuntia milpa alta polysaccharaides were purified/fractionated by DEAE-Sepharose CL-6B and Sepharose CL-6B chromatography to obtain fractions WSP1 and WSP3 and subfraction from fraction WSP2 WSP2a. Response surface analysis based on central composite design was employed to examine effects of extraction temperature and time and liquid/material ratio on Opuntia milpa alta polysaccharaide extraction. Besides, WSP1, WSP3 and WSP2a were analyzed for monosaccharide composition and anticoagulant activity. Results showed that two-time extraction for 3.63 h each time at 75 ℃ and a liquid/material ratio of 3.42 mL/g gave an optimal crude Opuntia milpa alta polysaccharaide yield, reaching up to 0.655% (calculated on the basis of wet weight). WSP1, WSP3 and WSP2a exhibited weight average molecular weights of 2.32×106, 1.24 ×106 and 7.92×106, respectively. The predominant monosaccharide in WSP1 was galactose. WSP2a consisted of 6.3% of rhamnose, 32.3% of arabinose, 12.9% of xylose, 1.5% of mannose, 4.8% of glucose, 37.1% of galactose, 0.7% of glucuronic acid and 4.4% of galacturonic acid. The monosaccharide composition of WSP3 mainly consisted of arabinose, xylose, rhamnose and trace of glucose, mannose and uronic acid. WSP2a and WSP3 showed obvious anticoagulant activity.

Key words: Opuntia milpa alta, polysaccharide, extraction, purification, anticoagulation