Antar Nasr El-Banna

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.

Genus Carissa represents several species that are reported to be of great phyto-medicinal and ethnopharmacological value. However, Carissa macrocarpa is relatively understudied. Furthermore, environmental conditions such as seasonal changes are known to affect the phytochemical composition of medicinal plants. Therefore, this study aimed to investigate the phytochemical composition and biological activity of the leaf extracts of C. macrocarpa in the summer and winter seasons. The phytochemical screening of C. macrocarpa leaves showed positive results for a variety of phytochemicals, such as alkaloids, tannins, phenols, naphthoquinones, flavonoids, saponins, steroids, proteins, carbohydrates, mucilage, gum and resin. The methanolic extract was evaluated for its antibacterial activity against Escherichia coli and Staphylococcus aureus using the agar well diffusion method. The winter leaf extract was distinguished for its potential antibacterial activity against both bacterial strains with inhibition zones (mm) of 8.17 ± 1.04 and 6.83 ± 0.58 at 10 mg/mL. The antioxidant activity of the leaf extracts was evaluated using the 2, 2′-diphenyl-1-picrylhydrazyl (DPPH) assay. The percentage scavenging activities of the different extracts were significantly greater than that of the control. Furthermore, at 15, 30, 60, 120 and 240 µg/mL, the percentage scavenging activities of the winter methanol leaf extract were 74.65, 78.31, 85.45, 90.02 and 95.68%, and those of the summer one were 71.66, 73.57, 84.05, 88.22 and 96.28%, respectively, indicating that the methanol leaf extract had greater percentage scavenging activity in winter than in summer. In winter, the IC₅₀ value of the methanol leaf extract (0.67 µg/mL) was lower than that of ascorbic acid (8.26 µg/mL). It is concluded that winter is the optimal season to harvest leaves of C. macrocarpa for medicinal use. To the best of our knowledge, this is the first report that relates the phytochemical composition and medicinal properties of C. macrocarpa to changes in seasons. The results obtained are promising, and this species should be further explored to decipher its pharmacological worth.

Microbial contamination is a common problem that causes significant losses in plant micropropagation systems. The present study reports on the identification and control of bacterial contaminants in banana in vitro cultures. Twelve isolates belonging to Bacillus pumilus (S2), Bacillus subtilis (R2 and M4), Geobacillus stearothermophilus (S1, S3, S4, P2, M3 and R3) and Paenibacillus spp. (P1, R1 and M2) were identified by sequencing of 16S rRNA, gyrA or gyrB genes. Antibiotic susceptibility testing was performed with the disk diffusion method on bacterial isolates using 36 antimicrobial agents. Some antibiotics, notably Ticarcillin, Penicillin, Ampicillin, Cefazolin and Imipenem, had a broader range of bactericidal activity than others did. When contaminated axillary shoot cultures of banana were treated with 100 or 200 mg·L⁻¹ of ticarcillin, ampicillin or penicillin the bacteria were eliminated, but a reduction in shoot multiplication and growth was observed. These findings contribute to minimizing the losses in the commercial micropropagation of banana.

Potentially toxic elements (PTEs)-induced genotoxicity on aquatic plants is still an open question. Herein, a single clone from a population of water hyacinth covering a large distribution area of Nile River (freshwater) was transplanted in two drainage water resources to explore the hazardous effect of PTEs on molecular, biochemical and anatomical characters of plants compared to those grown in freshwater. Inductivity Coupled Plasma (ICP) analysis indicated that PTEs concentrations in water resources were relatively low in most cases. However, the high tendency of water hyacinth to bio-accumulate and bio-magnify PTEs maximized their concentrations in plant samples (roots in particular). A Random Amplified Polymorphic DNA (RAPD) assay showed the genotoxic effects of PTEs on plants grown in drainage water. PTEs accumulation caused substantial alterations in DNA profiles including the presence or absence of certain bands and even the appearance of new bands. Plants grown in drainage water exhibited several mutations on the electrophoretic profiles and banding pattern of total protein, especially proteins isolated from roots. Several anatomical deteriorations were observed on PTEs-stressed plants including reductions in the thickness of epidermis, cortex and endodermis as well as vascular cylinder diameter. The research findings of this investigation may provide some new insights regarding molecular, biochemical and anatomical responses of water hyacinth grown in drainage water resources.