Micromorphology and biological activities of leaves and stem bark of Diospyros villosa (L.) De Winter.
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Date
2021
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Abstract
Review Article: The genus Diospyros consists of many species which are distributed
throughout the world. There is no elaborate information about the holistic importance of the
plants. This review aims to delve for more information about the usefulness of the plants for
humans. A detailed study of the genus Diospyros with a targeted focus on Diospyros villosa
(L.) De Winter plant was carried out information on the plants’ morphology was taken as
observed during harvest. Other information with respect to geographical distribution,
secretory structures, chemical composition, embedded bioactive constituents and the
associated mechanism of action of the bioactive constituents were acquired. The genus
Diospyros yields products of medicinal importance throughout the world. This study gives
some detailed information about the genus Diospyros as well as the potential use of the
species as functional medicinal plants with bioactive compounds.
Manuscript 1: This study evaluated the phytochemical constituents, antioxidant and
antimicrobial potentials of Diospyros villosa (L.) De Winter leaves and stem bark. The
extracts were obtained using different media (methanol, chloroform and hexane). DPPH and
FRAP methods were used to investigate the antioxidant potentials of the crude extracts. The
antimicrobial potency of Diospyros villosa extracts against five pathogenic bacteria was
determined using MIC, MBC and agar well diffusion methods. Flavonoids, alkaloids and
phenols were identified in D. villosa extracts. The mean concentrations of methanol extracts
Diospyros villosa leaves and stem against DPPH providing 50% inhibition were 9.53 ± 0.25
μg ml-1 and 9.52 ± 0.30 μg ml-1 respectively. The methanolic leaves extracts further showed
promising antimicrobial activity against Klebsiella pneumonia, Pseudomonas aeruginosa,
methicillin-resistant Staphylococcus aureus and Staphylococcus aureus with inhibition zones
which are almost as high as the control. The antimicrobial methods also demonstrated that the
leaves and stem bark extracts had wide antimicrobial abilities. The results revealed that D.
villosa leaves and stem bark contain reasonable amount of bioactive compounds. Hence,
these compounds may serve as natural antioxidants and antibacterial agents for the treatment
of bacterial infections and diseases.
Manuscript 2: Nanoparticles are synthesized through wet chemical techniques. Meanwhile,
the chemicals used often are toxic and flammable. While considering safe substances,
Diospyros villosa leaves and stem bark are both observed to be suitable for the biosynthesis
of silver nanoparticles. In this research study, we described a less expensive and
environmental-friendly technique for the biosynthesis of silver nanoparticles from silver
nitrate (AgNO3) solution and Diospyros villosa extracts. The obtained silver nanoparticles
were characterized using the UV-vis absorption spectroscopy, FT-IR, EDX, SEM and TEM,
DPPH scavenging ability, ferric reducing antioxidant potential, antimicrobial susceptibility
and quorum sensing inhibition tests. The biosynthesized silver nanoparticles showed good
antibacterial activity against Escherichia coli, Staphylococcus aureus, Staphylococcus
epidermis and Enterococcus faecalis. The D. villosa nanoparticles demonstrated potential
antioxidant and quorum sensing inhibition and may thus represent a source of antioxidant as
well as quorum sensing inhibition candidate for infection and disease control.
Manuscript 3: The structural adaptation, histological compatibility and ecological functions
of trichomes in Diospyros villosa, however remain largely unclear. This study aimed to
interpret the structure and histochemical analysis of the leaves and stem bark of Diospyros
villosa using light and electron microscopy and different histochemical tests as well as to
elucidate the composition of the secretory products. Trichome density and length were also
determined in three developmental stages of the leaves. The results of histochemical tests also
revealed the presence of alkaloids and phenolic compounds which are medicinally important
and used to treat multiple ailments.
Manuscript 4: Diospyros villosa is traditionally used for processing anti-bacterial properties.
Its cytotoxic effects have not been studied before. Therefore, this study aimed to examine the
nutritional properties as well the cytotoxic effects of D. villosa. The leaves and stem barks
were subjected to three different extraction methods (methanol, chloroform and hexane) and
their nanoparticles were synthesized at two different temperatures (room temperature and at
80 ºC). Thereafter, extracts were assessed using the associated AOCC protocols, for their
nutritional content (moisture, fibre, proteins, lipid, ash and hydrolysable carbohydrates).
Diospyros villosa extracts and their corresponding nanoparticles were then incubated
overnight with cancerous and noncancerous cell lines to evaluate their cytotoxic potential.
Description
Doctoral Degree. University of KwaZulu-Natal, Durban.