Introduction
The presence of natural products in animals, plants, and minerals plays
a vital role in the field of medicinal chemistry; therefore, researchers
from antiquity are working on the extraction, isolation, identification,
biological activities, and many properties of these natural organic
products. Conventional medicines depend on phytochemical-rich plant
extracts to cure many diseases because medicines obtained from natural
sources are less toxic and have fewer side effects than synthetic
medicines [1]. For the remedy of many health issues, to remove pain
and discomfort, such as fragrance and flavor in food, everyone depends
on the plant kingdom for their needs, and medicinal plants play a vital
role in developing countries. Medicinal plants are the best source for
the discovery of new compounds that lead to new drugs [2]. Medicinal
plants of the Moraceae family are known for their versatile applications
in many fields such as agriculture, cosmetics, food, and
pharmaceuticals. One example of the family Moraceae is Morus alba
(mulberry), which is the most commonly used medicinal plant in Asia,
especially in China. Mulberry is highly produced in China and grows
throughout many regions such as Asia, Africa, America, Europe, and
India. The leaves of mulberry are only known for sericulture. But the
leaves are not used in sericulture but can be used as medicines as well
[3]. Mulberry is a rich source of many bioactive compounds such as
flavonoids, amino acids, vitamins, polysaccharides, and steroids, which
are used for the treatment of many infections and internal diseases.
Among these components, flavonoids have attracted more attention in
recent studies because of their anti-inflammatory, anti-aging, and
anti-hyperglycemic activities. [4,5]. Flavonoids belong to the
polyphenolic family and incorporate at least 6000 molecules, primarily
divided into phlobaphenes, aurones, isoflavonoids, flavones, flavonols,
and anthocyanins [6]. Flavonoid compounds commonly found in mulberry
are kuwanon (flavons), sangenon (flavanols), rutin (flavons), quercetin
(flavonols), and catechins (flavanols).
Plants have an amazing tendency to identify changes in the environment,
and then the rapid response to increases the opportunity and lowers the
risk. The basic need to respond to these changes is the integration of
growth, development, and metabolism, which leads to the evolution of
many other mechanisms to regulate cellular functions. One of the
mechanisms is glycosylation, which involves a large multigene family of
glycosyltransferases (GTs). Glycosyltransferases can identify lipophilic
small molecules, including hormones and secondary metabolites, as well
as biotic and abiotic toxins in the environment [7,8]. Glycosylation
of flavonoids increases their solubility and stability in plants.
Flavonoids exist mainly in their glycosylated forms in plants. The final
step in the biosynthesis of these glycosides is glycosylation, which
plays a variety of roles in plant metabolism. Glycosyltransferases
(GTFs) establish natural glycosidic linkages. They catalyze the transfer
of saccharide moieties from an activated nucleotide sugar (also known as
a glycosyl donor) to a nucleophilic glycosyl acceptor molecule, the
nucleophile of which can be oxygen-, carbon-, nitrogen-, or
sulfur-based. GTFs play an important role in glycosylation, and it is
important to understand the chemistry of these enzymes in mulberry
leaves.