Isolation, purification and antioxidant activity of polysaccharides from the leaves of maca (Lepidium Meyenii)

Maca (Lepidium meyenii), an annual or biennial plant of family of Brassicaceae, mainly grows in the Andes region of Peru where the altitude is between 3500 and 4500 m above sea level. This area is characterized by freezing temperature, intense sunlight, fierce winds, barren, androcky terrain. Themacahypocotylshave been used as both foodstuff and folk medicine in the Andes for over 2000 years. It has been recommended as a safe edible food by the FAO in 1992, and has been promoted for global cultivation. Up to now, a variety of active components have been found in maca, including macaene and macamides, glucosinolates, alkaloid sterols and flavonolignans, and polysaccharides.

Plant polysaccharides gained the attention in medicine due to their biological activities such as antioxidant, immunomodulation, antidiabetic, anti-tumor, antibiotic, and anti-inflammatory. Recently, an increasing number of studies have focused on the structural characterization and activities of maca polysaccharides obtained from maca hypocotyls. For example, the polysaccharides of Lepidium meyenii (LMPs) were extracted by hot water, and four LMPs were obtained through increasing the concentration of ethanol in the process of polysaccharide precipitation. Wang et al. reported that a polysaccharide (MP21) isolated and purified from maca hypocotyls had an average Mw of 3.68 × 105 Da, and the MP21 was mainly composed of rhamnose, arabinose and galactose in a molar ratio of 1:4.84:5.34. Zhang, et al. had been revealed the structural features of MC-1 (a novel polysaccharide) from maca hypocotyls. It was reported that the polysaccharides from maca hypocotyls showed antioxidant, anti-fatigue, and immunomodulatory activities. Recently, it is proved that maca polysaccharide (MP-1) possesses a protective effect on Hep-G2 cells and alcoholic liver oxidative injury in mice. However, few studies have focused on the purified polysaccharides of maca leaves and their biological activities. The maca leaves accounting for 20–40% (m/m, dry weight) of total biomass of maca were ignored and wasted, which led to the waste of maca resources.

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