Phytochemicals from Pterocarpus angolensis DC and Their Cytotoxic Activities against Breast Cancer Cells

Pterocarpus anglonesis DC is an indigenous medicinal plant belonging to the Pterocarpus genus of the Fabaceae family. It is used to treat stomach problems, headaches, mouth ulcers, malaria, blackwater fever, gonorrhea, ringworm, diarrhea, heavy menstruation, and breast milk stimulation. Column chromatography of the stem bark extracts resulted in the isolation of eight compounds, which included friedelan-3-one (1), 3α-hydroxyfriedel-2-one (2), 3-hydroxyfriedel-3-en-2-one (3), lup-20(29)-en-3-ol (4), Stigmasta-5-22-dien-3-ol (5), 4-O-methylangolensis (6), (3β)-3-acetoxyolean-12-en-28-oic acid (7), and tetradecyl (E)-ferulate (8). The structures were established based on NMR, IR, and MS spectroscopic analyses. Triple-negative breast cancer (HCC70), hormone receptor-positive breast cancer (MCF-7), and non-cancerous mammary epithelial cell lines (MCF-12A) were used to test the compounds' cytotoxicity. Overall, the compounds showed either no toxicity or very low toxicity to all three cell lines tested, except for the moderate toxicity displayed by lupeol (4) towards the non-cancerous MCF-12A cells, with an IC50 value of 36.60 μM. Compound (3β)-3-acetoxyolean-12-en-28-oic acid (7) was more toxic towards hormone-responsive (MCF-7) breast cancer cells than either triple-negative breast cancer (HCC70) or non-cancerous breast epithelial (MCF-12A) cells (IC50 values of 83.06 vs. 146.80 and 143.00 μM, respectively).

The Potential of Rhizobacteria to Mitigate Abiotic Stress in Lessertia frutescens

Lessertia frutescens is a multipurpose medicinal plant indigenous to South Africa. The curative ability of the medicinal plant is attributed to its rich phytochemical composition, including amino acids, triterpenoids, and flavonoids. A literature review of some of the phytochemical compounds, particularly amino acids, in L. frutescens shows a steady decrease in concentration over the years. The reduction of the phytochemical compounds and diminishing biological activities may be attributed to drought and salt stress, which South Africa has been grappling with over the years. Canavanine, a phytochemical which is associated with the anticancer activity of L. frutescens, reduced slightly when the plant was subjected to salt stress. Like other legumes, L. frutescens forms a symbiotic relationship with plant-growth-promoting rhizobacteria, which facilitate plant growth and development. Studies employing commercial plant-growth-promoting rhizobacteria to enhance growth and biological activities in L. frutescens have been successfully carried out. Furthermore, alleviation of drought and salt stress in medicinal plants through inoculation with plant growth-promoting-rhizobacteria is well documented and effective. Therefore, this review seeks to highlight the potential of plant-growth-promoting rhizobacteria to alleviate the effect of salt and drought in Lessertia frutescens.

Green Chemistry in action: towards sustainable production of Gold nanoparticles

This study reports the synthesis of gold nanoparticles from a gold precursor salt (HAuCl4·3H2O) using Moringa oleifera bark broth, a cheap renewable material, without adding external surfactant, capping agent or template. Biomolecules responsible for reducing Au3+ to Au0 and stabilization of the resulting nanoparticles were extracted from the bark, and the synthesis was monitored for precursor concentration, percentage broth, pH of reaction media and reaction time. The biosynthesized nanoparticles were characterized using spectroscopic (FTIR and UV-Vis) techniques, advanced microscopic imaging (HRTEM, SEM/EDS), and Zeta potential measurements. Distinct color change from yellow to wine red was observed, indicative of the formation of gold particles at nanoscale. The SPR band was found at around 550 nm, in agreement with conventional synthetic protocols. The particles were stable with a net negative surface charge (–20 mV), a contribution associated with the protein nature of the broth. Addition of Pb2+ to the polydisperse nanoparticle suspension resulted in a color shift, to a faint blue color, coupled with a corresponding SPR shift to higher wavelengths, depending on the concentration of Pb2+ added. This color change is attributed to the aggregation of the colloidal particles due to complexation effects of the metal ions with the biomolecules on the surface of the nanoparticles.

Adaptation and detoxification mechanisms of Vetiver grass (Chrysopogon zizanioides) growing on gold mine tailings

Vetiver grass (Chrysopogon zizanioides) was investigated for its potential use in the rehabilitation of gold mine tailings, its ability to extract and accumulate toxic metals from the tailings and its metal tolerant strategies. Vetiver grass was grown on gold mine tailings soil, in a hothouse, and monitored for sixteen weeks. The mine tailings were highly acidic and had high electrical conductivity. Vetiver grass was able to grow and adapt well on gold mine tailings. The results showed that Vetiver grass accumulated large amounts of metals in the roots and restricted their translocation to the shoots. This was confirmed by the bioconcentration factor of Zn, Cu, and Ni of >1 and the translocation factor of <1 for all the metals. This study revealed the defense mechanisms employed by Vetiver grass against metal stress that include: chelation of toxic metals by phenolics, glutathione S-tranferase, and low molecular weight thiols; sequestration and accumulation of metals within the cell wall that was revealed by the scanning electron microscopy that showed closure of stomata and thickened cell wall and was confirmed by high content of cell wall bound phenolics. Metal induced reactive oxygen species are reduced or eliminated by catalase, superoxide dismutase and peroxidase dismutase.

Near-infrared spectroscopy and chemometrics for rapid profiling of plant secondary metabolites

In this study, near-infrared (NIR) spectroscopy, in combination with chemometrics, was used as a rapid tool for determining if exposure to contamination from mine tailings influences the matrices of the specimens, compared to those from natural populations. Principal component analysis (PCA) plots were made from the chemometric models obtained to establish if season of harvest, geographical origin, and level of soil contamination play a determining role in the chemical profiles of the individual specimens harvested from mine sites or natural populations. The random distribution on PCA score plots corroborated the intraspecies variation of Lippia scaberrima previously observed by gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS) essential oil profiles. Clustering according to the season and origin of the individual plants confirmed that the geographic location and the season of harvest influence the chemical profiles of L. scaberrima. The NIR data could not be correlated with the level of soil contamination to which the specimens were exposed. The PCA scores and loadings plots obtained from NIR data of Searsia pendulina suggest that the species is tolerant to pollution from mine tailings. Although separation was obtained in a three-component PCA model between specimens sampled during different seasons, some clustering was observed by specimens from the same geographical origin.