The biosynthesis of silver nanoparticles (AgNPs) from Diospyros villosa leaves and stem bark extracts is described. The stem bark AgNPs of D. villosa synthesized at 80 °C (S80) showed good scavenging activity with a lower IC50 value of 8.75 µg·mL−1 compared to ascorbic acid (9.58 µg·mL−1). The total phenol content of the S80 AgNPs was measured and found to be 10.22 ± 0.14 mg.g−1 gallic acid equivalence (GAE). Bacterial growth inhibition (% GI) and violacein inhibition (% VI) of 10.08% and 58.83%, respectively, was observed against C.subtsugae CV017 with leaf AgNPs synthesized at 80 °C (L80) at 80 μg·mL−1. Stem bark AgNPs synthesized at room temperature (SRT) also indicated % GI of 13.83% and % VI of 65.97% against C. subtsugae CV017 at 160 μg·mL−1. Leaf AgNPs of D. villosa synthesized at room temperature (LRT), showed % GI of 29.07% and % VI of 56.53%, respectively, against C. violaceum ATCC 12472 at 320 μg·mL−1. The L80 and SRT at 160 μg·mL−1 and LRT at 320 μg·mL−1 may be considered as potential QS inhibitors following their activity against C. subtsugae CV017 and C. violaceum ATCC 12472, respectively. Therefore, D. villosa represents a potential source of antioxidants as well as an anti-quorum sensing therapeutic candidate for the control of Gram-negative bacterial infections.

This study aimed to evaluate the phytochemical components, antioxidant capacity, and antimicrobial effects of Diospyros villosa (L.) De Winter leaves and stem bark. The extracts were obtained using different media (methanol, chloroform, and hexane). The DPPH and FRAP methods were used to assess the antioxidant activity and the Folin–Ciocalteu method was used to determine the total phenolic contents of the crude extracts. The antimicrobial effects of the extracts against five pathogenic bacteria were determined using the MIC, MBC, and agar-well diffusion methods. Flavonoids, alkaloids, and phenols were identified in the D. villosa extracts. The mean concentrations of the methanolic leaf and stem-bark extracts against DPPH providing 50% inhibition were 9.53 ± 0.25 μg·mL−1 and 9.52 ± 0.30 μg·mL−1, respectively. In addition, the total phenolic content within the test range of concentrations was found to be 28.45 ± 0.50 mg of gallic acid equivalent per g of sample extract [mg·g−1 (GAE)] (methanolic leaf extract) and 4.88 ± 0.36 mg·g−1 (GAE) (methanolic stem-bark extract). The methanolic leaf extracts further showed promising antimicrobial activity against Pseudomonas aeruginosa, Klebsiella pneumonia, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus with inhibition zones of 18.0 ± 0.58, 23.5 ± 0.58, 20.0 ± 0.88, and 17.0 ± 2.0 mm, respectively which were comparable to the control (gentamicin and streptomycin). The results suggest that bioactive compounds are abundant in D. villosa leaves and stem bark and could serve as a potential source of natural antioxidants as well as an antibacterial agent for the treatment of pathogenic bacterial infections.

Diospyros villosa is a perennial species prominently acknowledged for its local medicinal applications. The native utilisation of this species in traditional medicine may be ascribed to the presence of secretory structures and their exudate (comprised of phytochemicals). However, the morphological nature and optical features of the secretory structures in D. villosa remain largely unclear. This study was directed to ascertain the occurrence and adaptive features of structures found within the leaves and stem bark of D. villosa using light and electron microscopy techniques. The current study notes the existence of trichomes, and other secretory structures were noted. SEM indicated the presence of non-glandular hirsute trichomes with bulky stalk on both leaves and stem surfaces. Transverse stem sections revealed the existence of crystal idioblasts. Moreover, the presence of the main phytochemical groups and their localisation within the foliage and stem bark was elucidated through various histochemical tests. The trichomal length and density were also assessed in leaves at different stages of development. The results indicated that the trichomal density at different stages of development of the D. villosa leaves and stem bark was not significantly different from one another, F(3,39) = 1.183, p = 0.3297. The average length of the non-glandular trichomes in the emergent, young and mature leaves, as well as in the stem, was recorded to be 230 ± 30.6 µm, 246 ± 40.32 μm, 193 ± 27.55 µm and 164 ± 18.62 µm, respectively. The perimeter and circumference of the observed trichomes in the developmental stages of D. villosa leaf and the stem bark were not statistically different, F(3,39) = 1.092, p = 0.3615. The results of histochemical tests showed the existence of phenols alkaloids, which are medicinally important and beneficial for treatment of diseases. The findings of this study, being reported for the first time may be considered in establishing microscopic and pharmacognostic measure for future identification and verification of natural herbal plant. Trichomal micromorphology and histological evaluations could be utilised as a tool for appropriate description for the assessment of this species.

Diospyros villosa is traditionally used for an anti-bacterial property. 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 °C). 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. The nutritional analysis revealed that both young and mature leaves were rich sources of protein having values of 14.95% and 11.37% respectively. The moisture content was observed to be higher in all the leaf types (8.54 ± 0.75%, 9.67 ± 0.98% and 7.40 ± 0.80%) compared to the stem (2.13 ± 0.07%) respectively. The MTT cytotoxicity assay showed that the cell viability of MCF-7 cell lines was significantly lower when exposed to hexane and chloroform leaves extracts of D. villosa (IC50 of 26.64 and 26.07 µg mL−1) respectively, compared to camptothecin (36.54 µg mL−1). Similarly, the MCF-7 cell viability was observed to be significantly lower when exposed to hexane and chloroform stem extracts of D. villosa (IC50 of 24.57 and 3.92 µg mL−1), compared to camptothecin (36.54 µg mL−1). The cell viability of A549 cell lines was also found lower when exposed to the hexane and chloroform extracts (IC50 of 7.76 and 4.59 µg mL−1) compared to camptothecin (IC50 of 19.26 µg mL−1). Furthermore, the viability of A549 cell lines was found lower when exposed to hexane and chloroform stem extracts of D. villosa (IC50 of 10.67 and 5.35 µg mL−1) compared to camptothecin (19.26 µg mL−1). The biosynthesized nanoparticles further displayed an anticancer activity with an IC50 value of 4.08 µg mL−1 when compared to the control (36.54 µg mL−1). However, the HEK293 cell viability was observed to be significantly higher on exposure to hexane stem extracts of D. villosa (IC50 of 158.5 µg mL−1) compared to camptothecin (IC50 of 14.77 µg mL−1). Therefore, Diospyros villosa leaves, stem bark and nanoparticles synthesized showed high potential for being considered as a candidate for an anti-cancer regimen.