Evaluation of bioactive compound contents in 50 varieties of mulberry leaves originating from different regions

Bioactive ingredients found in mulberry leaves have many medical and health promoting functions including antioxidant, anti-anxiety, anti-depressant, and anti-allergy. In order to better utilise the bioactive potential of mulberry resources, we determined the levels of 1-deoxynojirimycin (DNJ), gamma-aminobutyric acid (GABA), tannins, flavonoids, and polysaccharides in 50 different varieties of mulberry leaves. The bioactive contents in mulberry leaves may vary across species or region of origin, thus we investigated six different species as well as mulberry leaves originating from Japan, Sri Lanka, Uzbekistan, and 11 different Chinese provinces or cities. We found that bioactive compounds greatly varied among the 50 mulberry leaves examined (DNJ, 32.51 ~ 154.11 mg/100 g; GABA, 122.88 ~427.12 mg/100 g; tannins, 0.45 ~ 1.49 g/100 g; flavonoids, 12.86 ~ 31.57 mg/g; and polysaccharides, 7.55 ~ 20.52 g/100 g). High amounts of DNJ were obtained in Shenglidaye variety, high amounts of GABA, tannins, and flavonoids were obtained in Huasang variety, and high amounts of polysaccharides were obtained in Ganluo variety. Different varieties of mulberry leaves were rich in bioactive compounds with significant variations in their levels. DNJ content in leaves depended on variety and place of origin, while GABA, tannin, and flavonoid contents in leaves depended on variety and species. Six mulberry varieties, including Huasang, Jiuwenlong, Shigu 11-6, Shenglidaye, Qinpifusang, and HuoSang were identified as good sources for further utilisation. Huasang and Shenglidaye varieties were especially rich in DNJ or GABA, and thus have high potential value. The evaluation of mulberry leaves resources can supply precious data for screening accessions containing high levels of individual DNJ, GABA, and other bioactive compounds for use in breeding programs, and food and pharma industries.