Flavonoid Levels and Antioxidant Capacity of Mulberry Leaves: Effects of Growth Period and Drying Methods.

Lei Hu,Qing Zhang,Cheng Wang,Xiang Guo,Xiaoyang Chen,Dekui Chen,Wei Zhou

doi:10.3389/fpls.2021.684974

Lei Hu, Qing Zhang + Show 5 more

Open Access

https://doi.org/10.3389/fpls.2021.684974

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Abstract

In recent years, various mulberry leaf dishes have gradually gained in popularity. The harvesting period of mulberry leaves and the preparation of dried samples are critical for the retention of flavonoid content and activity. In this study, changes in flavonoid levels in mulberry leaves during their growth period (3–6 months), and the effects of four different drying methods [sun drying (SD), air drying (AD), oven drying (OD), and freeze drying (FD)] on flavonoid accumulation and antioxidant capacity were determined. The results showed that mulberry leaves grown for 6 months had higher levels of flavonoids, and different drying methods could significantly affect the flavonoid levels and antioxidant capacity of the leaves. Air drying and FD were the best methods in terms of retaining the antioxidant activity of flavonoids, although AD had lower operating costs than FD in the production process. Therefore, to obtain a high flavonoid content and maximum antioxidant activity, AD is recommended for mulberry leaves.

Highlights

Mulberry (Morus alba L.) is a woody plant of the genus Morus in the family Moraceae (Wang et al, 2019)
The levels and antioxidant activity of flavonoids in mulberry leaves were affected by growth time and drying method
The optimal accumulation was observed in mulberry leaves that had a relatively long growth period or were in the early stage of environmental stress exposure

Summary

Introduction

Mulberry (Morus alba L.) is a woody plant of the genus Morus in the family Moraceae (Wang et al, 2019). Mulberry leaves are rich in nutrients and can be eaten as vegetables. The popularity of mulberry may be due to it being a rich source of active substances, such as vitamins, amino acids, carotene, flavonoids, alkaloids, and polysaccharides (Rodrigues et al, 2019). Flavonoids are widely found in various plants, fruits, vegetables, and beverages. Flavonoids can be divided into flavones, flavonols, flavanols, anthocyanins, and isoflavones (Winkel-Shirley, 2001), and are mainly present in food as glycosides and polymers (Heim et al, 2002). Rutin, quercetin 3-(6-malonylglucoside), and isoquercitrin have been identified as the major antioxidants in ethanol extracts of M. alba leaves (Katsube et al, 2006). Many flavonoids exert antioxidant and free radical scavenging activity, the ability to prevent

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