Application to classification of mulberry leaves using multivariate analysis of proton NMR metabolomic data.

Recently, NMR-based metabolomic analysis has been used to acquire information based on differentiation among biological samples. In the present study, we examined whether multivariate analysis was able to be applied to natural products and/or material field. Each extraction of 24 leaf samples, divided into six locations from the tip of the stem in each of four strains, was analyzed by pattern recognition methods, known as Principal Component Analysis (PCA) and Soft Independent Modeling of Class Analogy (SIMCA). Twenty-four extracts from mulberry leaf showed independent spectra by 1H NMR. The separation of leaf extraction data due to the difference at six locations was achieved in the PCA score plot as correlation PC1 (86.1%) and PC3 (4.6%) and showed two loading plots, suggesting classification by leaf position as an independent variable in the loading plot. Moreover, the difference among six locations clarified the seven highest discrimination powers by the SIMCA method. Meanwhile, the PCA score plot obtained classification by the variety of mulberry strains with three loading plots, but the SIMCA method did not give a peak by classification.

The relationship between 1-deoxynojirimycin content and alpha-glucosidase inhibitory activity in leaves of 276 mulberry cultivars (Morus spp.) in Kyoto, Japan.

The relationship between 1-deoxynojirimycin (DNJ) content and alpha-glucosidase inhibitory activity in mulberry (Morus) leaves is discussed. Mulberry leaves were collected from the Center for Bioresource Field Science, Kyoto Institute of Technology, Kyoto, Japan on 19 May, 9 July, and 9 August, 2003. Mulberry leaves were extracted with 75% ethanol. The inhibitory activity for rat intestinal crude enzyme was measured using maltose. The content of DNJ in the extracts was measured using HPLC. The mean DNJ content in the 0.04-0.06% range was high in collected samples. The inhibitory activities in July and August were higher (P < 0.01) than in May, and the activity in July was higher (P < 0.01) than in August. A strong correlation (r = 0.901, r (2) = 0.811, n = 15) existed between DNJ content and alpha-glucosidase inhibition in leaves of Morus bombycis harvested in July. Similarly, correlation coefficients of the other mulberry varieties in July were higher than they were in May or August. The inhibitory activity and the DNJ content of Morus latifolia in August were lower than for any other mulberry variety. These results show that the high inhibitory cultivars harvested in July, except for M. latifolia, are more suited to products that contain high DNJ contents.