Antibacterial and Anti-Quorum Sensing Properties of Silver Nanoparticles Phytosynthesized Using Embelia ruminata.

The rise in antibiotic resistance (AR) poses an imminent threat to human health. Nanotechnology, together with mechanisms such as quorum sensing (QS), which relies on communication between bacterial cells, may decrease the selective pressure for AR. Thus, this study aimed to investigate the effectiveness of silver nanoparticles (AgNPs) synthesized at room temperature (Rt) and 80 °C using Embelia ruminata leaf, stem-bark, and fruit extracts as antibacterial and anti-QS agents. The phytosynthesized AgNPs solutions were subjected to various characterization assays and assessed for their antibacterial activities. Quantitative QS assays were performed using Chromobacterium subtsugae CV017 and Chromobacterium violaceum ATCC 12472. Synthesized AgNPs were spherical-to-near-spherical in shape, poly-dispersed, and crystalline, with a size range of 21.06-32.15 nm. Fruit AgNPs showed stronger antibacterial activity than AgNPs from other plant organs against selected bacterial strains. In the QS assays, fruit 80 °C AgNPs demonstrated the most significant violacein inhibition in an assay performed using the short-chain acyl homoserine lactone CV017 biosensor, while the leaf and fruit Rt AgNPs demonstrated the most violacein inhibition in an assay performed using the long-chain acyl homoserine lactone ATCC 12472 biosensor. The investigations carried out in this study lay the groundwork for future innovative research into antibacterial and anti-QS strategies using E. ruminata.

The Foliar Anatomy and Micromorphology of Cyphostemma hypoleucum (Vitaceae).

Cyphostemma hypoleucum (Harv.) Desc. ex Wild & R.B. Drumm is a perennial climber, indigenous to Southern Africa, and belongs to the Vitaceae. Although there have been many studies of Vitaceae micromorphology, only a few taxa have been described in detail. This study aimed to characterize the micro-morphology of the leaf indumentum and determining its possible functions. Stereo microscope, scanning electron microscope (SEM), and transmission electron microscope (TEM) were used to produce images. Micrographs of stereomicroscopy and SEM showed the presence of non-glandular trichomes. In addition, pearl glands were observed on the abaxial surface using a stereo microscope and SEM. These were characterized by a short stalk and a spherical- shaped head. The density of trichomes decreased on both surfaces of leaves as the leaf expanded. Idioblasts that contained raphide crystals were also detected in tissues. The results obtained from various microscopy techniques confirmed that non-glandular trichomes serve as the main external appendages of the leaves. Additionally, their functions may include serving as a mechanical barrier against environmental factors such as low humidity, intense light, elevated temperatures, as well as herbivory and insect oviposition. Our results may also be added to the existing body of knowledge with regard to microscopic research and taxonomic applications.

Antidiabetic effects of Psidium x durbanensis Baijnath & Ramcharun ined. (Myrtaceae) leaf extract on streptozotocin-induced diabetes in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Psidium guajava L. leaves are used to treat diabetes in South African folkloric medicine and in other parts of the world. Psidium x durbanensis Baijnath & Ramcharun ined. (PD) is a natural sterile hybrid and congener of Psidium guajava that is expected to share the medicinal properties of the genus Psidium and is widely distributed in South Africa. AIM OF THE STUDY: This study investigates the antioxidant, antidiabetic effects, and mechanisms of action of hydro-methanolic leaf extracts of PD on streptozotocin-induced diabetes in rats. MATERIAL AND METHODS: Phytochemical constituents of hydro-methanolic extract of PD were analyzed by gas chromatography-mass spectrometry (GC-MS). Male Wistar rats 250-300 g body weight (BW) were rendered diabetic after a single intraperitoneal injection with streptozotocin, 45 mg/kg BW. The diabetic rats were treated with hydro-methanolic (20:80 v/v) leaf extracts of PD (400 mg/kg/BW) or subcutaneous injections of regular insulin (2.0U/kg/BW, bid) for 56 days. The body weights of the animals were recorded daily. Fasting blood glucose, glucose tolerance tests, and insulin resistance index were measured. The effects of the extracts on total superoxide dismutase, catalase, and reduced glutathione activities, histopathology, and gene expression of insulin receptor substrate 1 and glucose transporter 4 were determined in the liver, pancreas, and gastrocnemius muscles of the rats. RESULTS: In the acute toxicity studies, there were no signs of toxicity observed for PD up to 2000 mg/kg BW doses. Diabetic animals showed significant weight loss, elevated and reduced fasting blood glucose and insulin, respectively, impaired glucose tolerance and diminished antioxidant enzymes' activities compared to controls. Treatment with PD hydro-methanolic leaf extracts improved body weight, glucose tolerance, insulin resistance, and antioxidant enzymes but not plasma insulin in diabetic animals compared to controls, respectively. GC-MS analysis identified organic acids, alcohols, vitamins, terpenoids, and esters in the extracts. Treatment with PD improved glucose uptake by stimulating mRNA expression of GLUT 4 in gastrocnemius muscles of diabetic animals compared to the untreated control and also restored histological aberrations in the pancreas and liver of diabetic rats compared with the untreated control rats. CONCLUSION: Collectively, the present study suggests that treatment with PD leaf extracts significantly ameliorated diabetes symptoms and oxidative stress in rats, and these effects may be linked to the bioactive phytoconstituents present in the plant. This study further suggests that PD improves insulin resistance by increasing glucose uptake in gastrocnemius muscles in an insulin-independent manner.

New Alk(en)ylhydroxycyclohexanes with Tyrosinase Inhibition Potential from Harpephyllum caffrum Bernh. Gum Exudate.

This work presents the first report on the phytochemical investigation of Harpephyllum caffrum Bernh. gum exudate. A known cardanol, 3-heptadec-12'-Z-enyl phenol (1) and three new alk(en)ylhydroxycyclohexanes, namely, (1R,3R)-1,3-dihydroxy-3-[heptadec-12'(Z)-enyl]cyclohexane (2) (1S,2S,3S,4S,5R)-1,2,3,4,5-pentahydroxy-5-[octadec-13'(Z)-enyl]cyclohexane (3) and (1R,2S,4R)-1,2,4-trihydroxy-4-[heptadec-12'(Z)-enyl]cyclohexane (4) were isolated from the gum. The structures of the compounds were determined by extensive 1D and 2D NMR spectroscopy and HR-ESI-MS data. The ethanolic extract of the gum was found to be the most potent tyrosinase inhibitor with IC50 of 11.32 µg/mL while compounds 2 and 3, with IC50 values of 24.90 and 26.99 µg/mL, respectively, were found to be potential anti-tyrosinase candidates from the gum. Gum exudate may be a potential source for non-destructive harvesting of selective pharmacologically active compounds from plants. The results also provide evidence that H. caffrum gum may find application in cosmetics as a potential anti-tyrosinase agent.

Microeukaryotic Communities on the Fruit of Gardenia thunbergia Thunb. with a Focus on Pathogenic Fungi.

Woody fruit which stay on ornamental plants for a long time may present a risk of infection to other organisms due to the presence of pathogens on their surface. We compared the microbe communities on the fruit surfaces of garden ornamental Gardenia thunbergia Thunb. with those on other surfaces in the study region. As Gardenia fruit contain antifungal substances, the focus of this study was on the fungal communities that exist thereon. We used Illumina sequencing to identify Amplicon Sequence Variants (ASV) of the internal transcribed spacer 2 (ITS2) of the ribosomal RNA. The microbial communities of the Gardenia fruit are distinct from the communities from the surrounding environments, indicating a specialized microhabitat. We employed clustering methods to position unidentified ASVs relative to known ASVs. We identified a total of 56 ASVs representing high risk fungal species as putative plant pathogens exclusively found on the fruit of Gardenia. Additionally, we found several ASVs representing putative animal or human pathogens. Those pathogens were distributed over distinct fungi clades. The infection risk of the high diversity of putative pathogens represented on the Gardenia fruit needs to be elucidated in further investigations.

Identification of potential SARS-CoV-2 inhibitors from South African medicinal plant extracts using molecular modelling approaches.

The coronavirus is a group of viruses found in animals as well as humans and have been detected since the 1960s. However, a newly identified form, SARS-CoV-2, has triggered a recent pandemic of respiratory disease now called COVID-19. There is currently no specific antiviral drug for the treatment of this pandemic, with most treatment strategies focused on symptomatic management and supportive therapy. As such, several drug discovery efforts are ongoing for potent treatment agents, with medicinal plants gradually gaining prominence. Approximately 80% of the South African population use traditional medicines to meet their primary health care needs. The current study aimed to identify potential COVID-19 therapeutic agents from a list of 29 bioactive compounds isolated from commonly used South African medicinal plants using molecular docking and molecular dynamics. Molecular docking identified arabic acid from Acacia senegal and L-canavanine found in Sutherlandia frutescens as a potential inhibitor of SARS-CoV-2 3C-like main protease. Similarly, hypoxoside isolated from Hypoxis hemerocallidea and uzarin from Xysmalobium undulatum, were identified as a potential inhibitor of SARS-CoV-2 receptor binding domain and SARS-CoV-2 RNA-dependent polymerase. These four bioactive compounds exhibited favourable binding orientations characterized by strong molecular interactions within respective inhibitors binding pockets of the target enzymes. Molecular dynamics simulations revealed that the binding of the identified inhibitors are characterized by structural perturbations which favour the inhibitory potency of these bioactive compounds. Additionally, in silico pharmacokinetic assessment of the compounds demonstrated favourable anti-SARS-CoV-2 properties. Although not conclusive, further experimental exploration of these compounds could serve as a starting point for the discovery of novel SARS-CoV-2 therapeutic.

Elemental Distribution and Health Risk Assessment of the Edible Fruits of Two Ficus Species, Ficus sycomorus L. and Ficus burtt-davyi Hutch.

Edible fruits of two indigenous medicinal Ficus species (Ficus sycomorus L. and Ficus burtt-davyi Hutch) collected from eight different sites in South Africa were assessed for nutritional value, elemental concentration, and the possible risk associated with their consumption. The metal concentrations in the fruits and growth soil were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). The results showed elemental concentrations in the fruits to contribute significantly to recommended dietary allowances and were found to be in decreasing order of Ca > Mg > Fe > Zn > Mn > Cu > Cr and Ca Ëƒ Mg Ëƒ Fe Ëƒ Mn Ëƒ Zn Ëƒ Cu for both F. sycomorus and F. burtt-davyi fruits. The results for proximate composition of F. sycomorus fruits were (in %) 55.8 for moisture, 25.3 for carbohydrates, 5.6 for protein, 8.9 for fats, 55.8 for crude fiber, and 4.4 for ash; for F. burtt-davyi fruits, it was (in %) 78.9 for carbohydrates, 5.0 for protein, 8.4 for lipids, 4.0 for crude fiber, and 3.7 for ash. The health risk assessment showed target hazard quotient, and hazard indices for all the studied heavy metals in the fruits for all the sites were to be less than one and the target carcinogenic risk values to be within the acceptable regulatory cancer risk range. This study confirms that the fruits of F. sycomorus and F. burtt-davyi are safe for human consumption due to low non-carcinogenic and carcinogenic adverse health effects.

Cytotoxic activity of the bioactive principles from Ficus burtt-davyi.

Ficus burtt-davyi (Moraceae) is a medicinal plant species indigenous to Southern Africa. In this study, a phytochemical and cytotoxic investigation on F. burtt-davyi was conducted to evaluate its ethno-medicinal use. The phytochemical study of the fruits yielded triterpenoids (lupeol and α-amyrin). The cytotoxic evaluation was done on the methanolic extracts and selected compounds, lupeol, α-amyrin, lupeol acetate and (+)-catechin isolated from F. burtt-davyi stem bark and fruits. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assay was carried out against two human cancer cell lines, breast adenocarcinoma (MCF-7) and colorectal adenocarcinoma (Caco-2), and normal human embryonic kidney cells (HEK293). The methanol extract from the stem bark was significantly cytotoxic to MCF-7 and Caco-2 cell lines (p < 0.05) in a concentration-dependent manner with IC50 values of 6.6 and 8.1 µg mL-1, respectively relative to the control. Lupeol and (+)-catechin showed cytotoxic activity against MCF-7 cell lines with IC50 values of 22.6 and 29.8 µg mL-1, respectively and greater cytotoxic activity against Caco-2 cell lines with IC50 values of 10.7 and 9.0 µg mL-1, respectively. Data from this study suggests that F. burtt-davyi exhibits cytotoxicity with no significant inhibitory effects against HEK293. The results also indicate that (+)-catechin and lupeol, the most abundant bioactive principles in the stem bark, are responsible for the synergistic cytotoxic effects against tested human cancer cell lines. This study provides evidence on the pharmaceutical potential of the medicinal plant, F. burtt-davyi, as a chemotherapeutic agent against cancer.

Anti-adhesion potential of non-polar compounds and extracts from Ficus natalensis

Abstract Four triterpenoids, ergosta-4,6,8(14),22-tetraene-3-one 1, stigma-4-ene-3-one 2, 3β-hydroxy-21β-H-hop-22(29)-ene 3, sitosterol and a quinone, tectoquinone 4, were isolated from the leaf, stem bark and fruit extracts of Ficus natalensis subsp. natalensis, Moraceae, a medicinal fig found in Africa. The pure compounds 1-4 and crude extracts were tested for their antibacterial activity against five Gram-negative and seven Gram-positive strains and for their potential anti-biofilm activity. Antimicrobial susceptibility was observed with all pure compounds tested at 250 µg against the majority of Gram-negative and Gram-positive strains. The dichloromethane-soluble fruit extract was active against sensitive and resistant Staphylococcus aureus strains, Enterococcus faecalis and Staphylococcus xylosus. Compounds 2, 3 and 4 demonstrated broad-spectrum antibiotic effects against eight of the twelve bacterial strains tested. In the anti-biofilm assay, exposure to ethyl acetate, methanol and aqueous methanol leaf, stem bark and fruit extracts decreased adhesion with a biofilm reduction of ≥100% for all three tested organisms: Escherichia coli, Pseudomonas aeruginosa and S. aureus. The methanol leaf extract demonstrated the most potent anti-adhesion potential against E. coli (218% biofilm reduction). The greatest ability to decrease adhesion was observed with compounds 2, 3 and 5 against P. aeruginosa at the lowest concentration tested (100 µg ml−1).

NEW INSIGHTS INTO THE PRESENCE OF BILIRUBIN IN A PLANT SPECIES STRELITZIA NICOLAI (STRELITZIACEAE).

BACKGROUND: The fortuitous discovery of an animal pigment bilirubin found in the plant Strelitzia nicolai has opened an enormous number of questions regarding bilirubin's formation and its ultimate function in the human body. MATERIALS AND METHODS: A methodical review of bilirubin in humans and animals was carried out, information was gathered using published scientific journals, books and conference proceedings. Articles based on case studies of elevated levels of bilirubin were analysed thoroughly. RESULTS: Even though for numerous years bilirubin was assumed to be merely a desecrate product of the heme catabolic pathway by greatest, and a likely lethal compound at worst; statistics from the last few decades clearly shows that placidly high serum bilirubin levels are robustly related to have abundant beneficial effects on the human body. CONCLUSION: This study reveals new insights into the presence of the only animal pigment found in Strelitzia nicolai arils, the potential advantages of bilirubin found in a plant and its therapeutic value indications. This review hopes to resuscitate researchers' credence regarding bilirubin as a toxic compound.

Nutritional evaluation, bioaccumulation and toxicological assessment of heavy metals in edible fruits of FicussurForssk (Moraceae).

Ficussur (Moraceae) is an indigenous medicinal plant with a wide distribution in Africa. In this study, the nutritional potential fruit of this indigenous plant to meet domestic food demands and reduce food insecurity in KwaZulu-Natal. South Africa, was investigated. The proximate composition and concentrations of metals in the edible fruits collected from eight different sites in KwaZulu-Natal were determined to assess for nutritional value and the concentrations of metals in the growth soil was determined to evaluate the impact of soil quality on elemental uptake. The fruits contained high levels of moisture (88.8%) and carbohydrates (65.6%). The concentrations of elements in the fruits were found to be in decreasing order of Ca>Mg >Fe >Zn>Cu >Mn> Se with low levels of toxic metals (As, Cd, Co and Pb). This study shows that the consumption of the fruits of F. sur can contribute positively to the nutritional needs of rural communities in South Africa for most essential nutrients without posing the risk of adverse health effects.

CHEMICAL CONSTITUENTS AND IN VITRO ANTIOXIDANT ACTIVITY OF CRUDE EXTRACTS AND COMPOUNDS FROM LEAVES AND STEM BARK OF FICUS BURTT-DAVYI.

Ficus buit-davyi, (Moraceae), is an endemic species of South Africa. In this study, a phytochemical analysis of the leaves and stem bark of F. burt-davyi resulted in the isolation of five triterpenes (lupeol, lupeol acetate, ß-sitosterol, stigmasterol and campesterol), one carotenoid (lutein), a pheophytin (phytyl-7-ethyl-25- (methoxycarbonyl)-3,8,13,17-tetramethyl-26-oxo- 12-vinyl-17,18-dihydro-2,20-ethanoporphyrin- 1 8-propanoate or pheophytin a) and one flavonoid (+)-catechin). The in viti antioxidant study of the methanol extracts of leaves and stem bark, (+)-catechin and pheophytin a using the 1,1-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay, ferric reducing antioxidant power (FRAP) assay and hydrogen peroxide (H202) assay showed significantly higher (p < 0.05) antioxidant activity for the methanol extract of the stem bark than the leaves, with IC55 values (in µg/mL) of 58.28 ? 5.05 for DPPH, 46.09 ± 0.06 for FRAP and 151.03 ± 1.60 pg/mL for H202,. The results suggest that the plant can be used as a therapeutic agent in alternative medicine for oxidative stress related degenerative diseases.

Antibacterial and anti-biofilm activity of flavonoids and triterpenes isolated from the extracts of Ficus sansibarica Warb. subsp. sansibarica (Moraceae) extracts.

BACKGROUND: Ficus species are used in African traditional medicine in the treatment of a wide variety of ailments and diseases such as convulsive disorder, wound healing, gonorrhea, tuberculosis, diabetes, diarrhoeal infections, dysentery, malaria and HIV. The aim of this study was to isolate the phytochemical constituents in the plant and test them for their antibacterial activity. MATERIALS AND METHODS: The fruits, leaves and stem bark were extracted with organic solvents and the compounds in the extracts separated and purified by column chromatography before being identified by NMR spectroscopy and by comparison of the NMR data against values reported in the literature. The antibacterial activity of the pure compounds and extracts were tested using the disk diffusion method. RESULTS: Three triterpenes and three flavonoids: lupeol acetate (1); cycloart-23-ene-3,25-diol (2); ß-sitosterol (3); 5,7,4'-trihydroxyflavan-3-ol (4); epicatechin (5); and isovitexin (6) were isolated in this study. Antimicrobial activity was observed at 8 mg mL(-1) for Staphylococcus aureus ATCC 29213 with four of the six isolated compounds, with no activity being observed at 1 - 4 mg mL(-1) against Escherichia coli ATCC 25922, E. coli ATCC 35218 and S. aureus ATCC 43300. Epicatechin (5) was found to decrease adhesion of E. coli ATCC 25922 and S. aureus ATCC 29213. Decreased adhesion of S. aureus ATCC 29213 was also observed with 5,7,4'-trihydroxyflavan-3-ol (4) and isovitexin (6). CONCLUSIONS: The results of this study provide baseline information on F. sansibarica's potential validity in the treatment of infections associated with Gram-positive microorganisms.

Effect of traditional leafy vegetables on the growth of lactobacilli and bifidobacteria.

Traditional leafy vegetables, apart from being a staple in the diet of most of sub-Saharan Africa, are an essential part of traditional medicine and are used daily by traditional healers in the region to treat a wide variety of ailments. In this study, a batch culture technique was used to investigate whether 25 infusions from 22 traditional leafy vegetables stimulated the growth of Lactobacillus bulgaricus, Lactobacillus lactis, Lactobacillus reuteri and Bifidobacterium longum in pure culture. High performance liquid chromatography was used to determine the inulin content of the infusions. Sonchus oleraceus stimulated all four strains and Taraxacum officinale stimulated three strains. In total, 18 plants stimulated at least one of the four probiotic strains. The inulin content of the infusions varied between 2.5% and 3.6%, with Asparagus sprengeri containing the highest percentage. These results indicate that traditional leafy vegetables do stimulate the growth of the selected lactobacilli and bifidobacteria in pure culture and contain inulin. These infusions can now be tested for prebiotic potential using mixed culture systems or human hosts.

Translocation and accumulation of Cr, Hg, As, Pb, Cu and Ni by Amaranthus dubius (Amaranthaceae) from contaminated sites.

Phytoremediation is an emerging technology where specially selected and engineered metal-accumulating plants are used for bioremediation. This study was undertaken to evaluate the potential of Amaranthus dubius for phytoremediation of chromium (Cr), mercury (Hg), arsenic (As), lead (Pb), copper (Cu) and nickel (Ni). Locally gathered soil and plants of A. dubius were investigated for the metals from a regularly cultivated area, a landfill site and a waste water treatment site. Metals were extracted from the samples using microwave-digestion and analyzed using Inductively Coupled Plasma-Mass Spectroscopy. The mode of phytoremediation, effect of the metals on the plants, ability of the plant to extract metals from soil (Bioconcentration Factor) and the ability of the plants to move the metals to the aerial parts of the plants (Translocation Factor) were evaluated. The survey of the three sites showed that soils were heavily contaminated with Cr, Hg, Cu and Ni. These levels were far above acceptable standards set for soils and above the standards set for the Recommended Dietary Allowance. Specimens of A. dubius from the three sites showed that they could tolerate Hg, sequester it from the soil, and translocate it to the shoots. Cr could only be removed from the soil and stored in the roots, with limited amounts translocated to the aerial parts. Pb, As, Ni, and Cu have some degree of transportability from the soil to the roots but not to aerial parts. The ability of A. dubius to be considered for phytoremediation has to be viewed with caution because translocation of the metals to the aerial parts of the plant is limited.