Effects of topping on rhizome, and analysis of chemical composition, antioxidant activity and α-amylase and α-glucosidase inhibition of the aerial parts in Polygonatum cyrtonema

Polygonatum cyrtonema is a perennial plant, and it has long been used in traditional Chinese medicine for food and medicine. The medicinal part of P.cyrtonema is the rhizome; however, the aerial part has not been studied. To understand the effect of the topping of aerial parts on the yield and chemical components of rhizomes, as well as the chemical constituents, antioxidant, and in vitro hypoglycemic activities of the aerial stem, leave, and flower parts of P.cyrtonema, the present study was conducted. The results showed that compared to the control (CK) treatment, the topping of the aerial part increased rhizome weight gain coefficient (3.43) and the total saponin content (37.60 mg/g) significantly (P<0.01) than the CK treatment. The contents of total phenols and total flavonoids in PCL and PCF were significantly (P<0.01) higher than those in rhizomes; however, the polysaccharide content (10.47%) in PCR (whole rhizome) was higher than that in PCS (3.65%), PCL (5.99%), and PCF (4.76%) content. The protein and amino acid contents in PCS, PCL, and PCF were higher than those in rhizomes. The protein and amino acid contents in PCS, PCL, and PCF were higher than those in rhizomes. PCS, PCL, and PCF showed strong antioxidant activity (DPPH, ·OH, ABTS, and FRAP), which were better than traditional medicinal parts (the rhizome).In vitro hypoglycemic results showed that PCS, PCL, and PCF had certain inhibitory activities on α-amylase and α-glucosidase (66.25% and 52.81%), which were close to the hypoglycemic activity of rhizomes (67.96% and 52.22%). The leaf extracts also showed better inhibitory activity. To sum up, the topping measures can improve yield and total saponin content of the rhizomes from P.cyrtonema, which can be applied to improve production. The stems, leaves, and flowers had a much stronger antioxidant and hypoglycemic activities and higher the total polyphenols, flavonoids, proteins, and amino acid content. Therefore, stems, leaves, and flowers of Polygonatum can be fully developed according to different needs. they are typically used in animal feed, food storage and cosmetics.