Phenolic Analysis for Classification of Mulberry (Morus spp.) Leaves according to Cultivar and Leaf Age

Phenolic compounds in mulberry leaves harvested from three cultivars (Buriram 60, BR 60; Sakonnakhon, SK; and Khunphai, KH) at different leaf ages (tips, young, and old leaves) were identified and quantified using HPLC-DAD and HPLC-ESI/MS. A total of 13 phenolic compounds, which were mainly as caffeoylquinic acids and flavonol glycosides, were detectable. Predominant phenolic compounds were 5-O-caffeoylquinic acid (3.5–13.1 mg/g dry weight), 4-O-caffeoylquinic acid (1.3–2.4 mg/g dry weight), and quercetin-3-O-rutinoside (1.0–4.4 mg/g dry weight). Qualitative and quantitative differences in phenolic compounds in mulberry leaves were investigated among cultivars and leaf ages. Principal component analysis and hierarchical cluster analysis were used for classification of the mulberry leaves. Based on the similarity of phenolic compounds, mulberry leaves were clustered into three groups: (1) tips of leaves from all cultivars; (2) young and old leaves of mulberry cv. BR 60; (3) young and old leaves of mulberry cv. SK and KH. Therefore, according to phenolic compounds in mulberry leaves, tips of leaves from all cultivars should be intended for production of functional healthy foods.