Abstract
Mulberry (Morus alba L.) leaf, a “source of both medicine and food”, contains antioxidant ingredients such as flavonoids, alkaloids and polyphenols. The effects of 6-benzylaminopurine (6-BA) treatment on plant growth and flavonoid contents in mulberry leaves were investigated in this study. The expression of rutin (Rut), chlorogenic acid (ChA), isoquercitrin (IQ) and astragaloside IV (Ast) related genes in the flavonoid synthesis pathways was investigated in mulberry leaves. The results showed that 6-BA treatment significantly promoted mulberry differentiation and growth as well as, increased the numbers of new shoots and buds compared to the control. In addition, 30 mg/L 6-BA significantly increased the contents of Rut, IQ and Ast, and it strongly induced the expression of flavonoid biosynthesis-related genes, including flavonoid 3-O-glucosyltransferase (F3GT), 4-xoumarate-CoA ligase (4CL), phenylalanine (PAL) and chalcone synthase (CHS). The dietary risk assessment of mulberry leaves was based on hormone residues 5 days after treatment with 30 mg /L 6-BA, and the results showed that the dietary exposure risk of 6-BA was extremely low without causing any health concern. Thus, treatment with 30 mg/L 6-BA is a new method to improve the medicinal quality and development of high-value mulberry leaf foods without any potential risk.
Highlights
Mulberry (Morus alba L.) is a popular “affinal drug and diet” plant, and it is widely distributed in the provinces of southern China
During the culture period of 0–30 d, the number of new shoots and buds of mulberry seedlings gradually increased, and the number of new shoots of mulberry seedlings in the 30 mg/L 6-BA treatment group reached peak values at 15 d and was increased by 130% compared to the control treatment (Fig. 2C)
The number of buds of mulberry seedlings treated with 30 mg/L 6-BA reached peak values and was increased by 64% compared to the control treatment (Fig. 2D)
Summary
Mulberry (Morus alba L.) is a popular “affinal drug and diet” plant, and it is widely distributed in the provinces of southern China. The Ministry of Health of China has listed mulberry leaves as a plant resource that is "a source of both medicine and food". Leaf tea is usually derived from ordinary leaves, because it is not limited by materials, its output meets the supply. The materials of bud tea are derived from one bud and two leaves from the top of mulberry shoots (leaf bud and the two leaves immediately below it), and the production of bud tea is limited due to the precise requirements for these rare raw materials. Due to the increased demand for bud tea, new buds of mulberry seedlings are severely lacking, resulting in a shortage of supplies in markets (Li et al 2019; Hu et al 2020). It is necessary to increase the output and medicinal ingredients of mulberry leaves by exogenous hormone regulation
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