Phytochemistry of the mopane, Colophospermum mopane

The essential oil of Lactuca longidentata Moris and its antioxidant and antimicrobial activities

Lactuca longidentata Moris (Asteraceae) is an endemic species growing only on Mesozoic limestone of central Sardinia. In the present study, the essential oil of the epigeal part of the plant was analyzed by gas chromatography-mass spectrometry (GC/MS). The main volatile components were α-terpineol (27.64%) and limonene (25.8%). The essential oils showed a noteworthy ability of scavenging free radical species (1,1-diphenyl-2-picrylhydrazyl (DPPH) test systems) with a mean half maximal inhibitory concentration IC₅₀ of 32.24 μg/mL. More significant was the inhibition of lipid oxidation that corresponded to an activity 1.5 times lower than that of 2,6-bis(1,1-dimethylethyl)-4-methylphenol (BHT). The essential oil was also assayed on Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis, Escherichia coli, and Candida albicans by the microdilution broth method and was particularly active against B. subtilis, with a minimal inhibitory concentration (MIC) value of 100 μg/mL.

Polyphenolic compounds as electron shuttles for sustainable energy utilization

For renewable and sustainable bioenergy utilization with cost-effectiveness, electron-shuttles (ESs) (or redox mediators (RMs)) act as electrochemical "catalysts" to enhance rates of redox reactions, catalytically accelerating electron transport efficiency for abiotic and biotic electrochemical reactions. ESs are popularly used in cellular respiratory systems, metabolisms in organisms, and widely applied to support global lives. Apparently, they are applicable to increase power-generating capabilities for energy utilization and/or fuel storage (i.e., dye-sensitized solar cell, batteries, and microbial fuel cells (MFCs)). This first-attempt review specifically deciphers the chemical structure association with characteristics of ESs, and discloses redox-mediating potentials of polyphenolics-abundant ESs via MFC modules. Moreover, to effectively convert electron-shuttling capabilities from non-sustainable antioxidant activities, environmental conditions to induce electrochemical mediation apparently play critical roles of great significance for bioenergy stimulation. For example, pH levels would significantly affect electrochemical potentials to be exhibited (e.g., alkaline pHs are electrochemically favorable for expression of such electron-shuttling characteristics). Regarding chemical structure effect, chemicals with ortho- and para-dihydroxyl substituents-bearing aromatics own convertible characteristics of non-renewable antioxidants and electrochemically catalytic ESs; however, ES capabilities of meta-dihydroxyl substituents can be evidently repressed due to lack of resonance effect in the structure for intermediate radical(s) during redox reaction. Moreover, this review provides conclusive remarks to elucidate the promising feasibility to identify whether such characteristics are non-renewable antioxidants or reversible ESs from natural polyphenols via cyclic voltammetry and MFC evaluation. Evidently, considering sustainable development, such electrochemically convertible polyphenolic species in plant extracts can be reversibly expressed for bioenergy-stimulating capabilities in MFCs under electrochemically favorable conditions.

Characterization of the Primary Metabolome of Brachystegia boehmii and Colophospermum mopane under Different Fire Regimes in Miombo and Mopane African Woodlands

Miombo and Mopane are ecological and economic important woodlands from Africa, highly affected by a combination of climate change factors, and anthropogenic fires. Although most species of these ecosystems are fire tolerant, the mechanisms that lead to adaptive responses (metabolic reconfiguration) are unknown. In this context, the aim of this study was to characterize the primary metabolite composition of typical legume trees from these ecosystems, namely, Brachystegia boehmii (Miombo) and Colophospermum mopane (Mopane) subjected to different fire regimes. Fresh leaves from each species were collected in management units and landscapes across varied fire frequencies in the Niassa National Reserve (NNR) and Limpopo National Park (LNP) in Mozambique. Primary metabolites were extracted and analyzed with a well-established gas chromatography time-of-flight mass spectrometry metabolomics platform (GC-TOF-MS). In B. boehmii, 39 primary metabolites were identified from which seven amino acids, two organic acids and two sugars increased significantly, whereas in C. mopane, 41 primary metabolites were identified from which eight amino acids, one sugar and two organic acids significantly increased with increasing fire frequency. The observed changes in the pool of metabolites of C. mopane might be related to high glycolytic and tricarboxylic acid (TCA) rate, which provided increased levels of amino acids and energy yield. In B. boehmii, the high levels of amino acids might be due to inhibition of protein biosynthesis. The osmoprotectant and reactive oxygen species (ROS) scavenging properties of accumulated metabolites in parallel with a high-energy yield might support plants survival under fire stress.

Antibacterial activity of aqueous and methanol extracts of selected species used in livestock health management

CONTEXT

Salvadora persica L. (Salvadoraceae), Colophospermum mopane (J.Kirk ex Benth.) J. Léonard (Leguminosae) and Dichrostachys cinerea (L.) Wight & Arn. (Leguminosae) crude extracts are used by local farmers against many livestock infections with little or no side effects usually associated with synthetic antimicrobials. However, their efficacy has rarely been tested.

OBJECTIVE

These plants were tested for potential antibacterial activity against clinical isolates of Staphylococcus aureus ATCC33862 and Escherichia coli ATCC25922. Minimal inhibitory concentrations (MIC) of the crude plant extracts were determined.

MATERIALS AND METHODS

Aqueous and methanol extraction of 100 g each of the bark of C. mopane, roots of D. cinerea and leaves of S. persica was done by placing the samples in 250 mL of either water or methanol. Nutrient broth was used as growth medium for the bacteria, and McFarland standard for bacterial standardization. 2,3,5-Triphenyltetrazoliumchloride (TTC) was the indicator salt. Each of the aqueous and methanol extracts (100 μL) was tested. Gentamycin and ampicillin were the controls.

RESULTS

MIC of aqueous extracts ranged from 1.03-14.6 mg/mL against S. aureus, and from 12.1-34.3 mg/mL against E. coli. Methanol extracts ranged between 5.31 and 9.64 mg/mL against S. aureus, and between 7.86 and 13.6 mg/mL against E. coli. Aqueous and methanol extracts of S. persica were significantly higher (p < 0.05) than C. mopane and D. cinerea.

DISCUSSION AND CONCLUSION

Colophospermum mopane, S. persica and D. cinerea exhibited antibacterial activity, with methanol extracts performing better than aqueous extracts, justifying use as ethnoveterinary medicine. Further study to isolate the active components should be pursued.

Labdane and Clerodane Diterpenoids from Colophospermum mopane

Five labdane (1-5), an isolabdane (6), and five clerodane diterpenoids (7-11), were isolated from seeds, husks, and leaves of Colophospermum mopane. Compounds 1-3 and 6-9 are new, and their structures were elucidated by means of physical data analysis (1D and 2D NMR, HRESIMS). The absolute configurations of 1, 7, and 10 were determined by single-crystal X-ray diffraction with Cu Kα radiation. For compounds 2 and 6, the absolute configurations were established by the modified Mosher's method and corroborated by comparison of experimental and calculated electronic circular dichroism spectra of their 3-p-bromobenzoate derivatives. The crude extracts and compounds were evaluated for antimicrobial activity. The leaf extract was the most active against Staphylococcus aureus (125 μg/mL). Compound 11 showed the best inhibitory activity, with minimum inhibitory values of 15.6 μg/mL against Escherichia coli and Staphylococcus aureus and 31.3 μg/mL against Enterococcus faecalis.

The Search for Antifungals from Amazonian Trees: A Bio-Inspired Screening

The anti-fungal activity of 60 extracts from 15 tree species in the French Guiana rainforest against human and wood-rotting fungi was studied. In this way (+)-mopanol (1) was isolated from the ethyl acetate extract of Peltogyne sp. (Caesalpiniaceae) wood. This work demonstrated that (1) the natural durability of wood can indeed guide the search for antifungal agents, (2) that extracts selected in this bio-inspired process exhibit a broad spectrum of antifungal activity and (3) that the method allows for the isolation of strongly active antifungals.

Differential effects of defoliation by mopane caterpillars and pruning by African elephants on the regrowth of Colophospermum mopane foliage

Plant responses to herbivory vary depending on herbivory type, yet the comparative effects of defoliation (e.g. by insects) and pruning (e.g. by large mammals) on a single tree species are poorly documented. We investigated this in the Northern Province of South Africa by comparing the regrowth of Colophospermum mopane trees previously defoliated by caterpillars or pruned by elephants, the two main browsers of C. mopane foliage. Shoots were up to 160% and 125% longer after natural (elephant) and simulated pruning and leaves ~25% longer in regrowth after natural pruning (n = 13–15 trees per treatment). Shoot density and chemical defences in leaves (tannin:protein ratio and total polyphenolic concentration) were, however, no different from control trees. Simulated defoliation resulted in statistically insignificant changes to regrowth in terms of leaf and shoot size (both slightly decreased) and shoot density (slightly increased). Natural (caterpillar) defoliation, however, resulted in regrowth with significantly decreased shoot and leaf size (about 50% and 20% of control lengths, respectively), as well as decreased leaf chemical defence. Shoot and leaf length were longer on trees flushing for the first time after pruning and late-season defoliation had a greater negative impact than mid-season defoliation. Despite the differences in regrowth characteristics after pruning and defoliation, mopane plants showed no apparent trade-off in investment between tolerance and resistance after either herbivory type, as neither regrowth nor chemical defence occurred at the expense of the other.

Flavan-3-ols: nature, occurrence and biological activity

Representing the most common flavonoid consumed in the American diet, the flavan-3-ols and their polymeric condensation products, the proanthocyanidins, are regarded as functional ingredients in various beverages, whole and processed foods, herbal remedies and supplements. Their presence in food affects food quality parameters such as astringency, bitterness, sourness, sweetness, salivary viscosity, aroma, and color formation. The ability of flavan-3-ols to aid food functionality has also been established in terms of microbial stability, foamability, oxidative stability, and heat stability. While some foods only contain monomeric flavan-3-ols [(-)-epicatechin predominates] and dimeric proanthocyanidins, most foods contain oligomers of degree of polymerization values ranging from 1-10 or greater than 10. Flavan-3-ols have been reported to exhibit several health beneficial effects by acting as antioxidant, anticarcinogen, cardiopreventive, antimicrobial, anti-viral, and neuro-protective agents. This review summarizes the distribution and health effects of these compounds.

Proanthocyanidin biosynthesis--still more questions than answers?

Proanthocyanidins, also known as condensed tannins, are oligomers or polymers of flavan-3-ol units. In spite of important breakthroughs in our understanding of the biosynthesis of the major building blocks of proanthocyanidins, (+)-catechin and (-)-epicatechin, important questions still remain to be answered as to the exact nature of the molecular species that undergo polymerization, and the mechanisms of assembly. We review the structures of proanthocyanidins reported over the past 12 years in the context of biosynthesis, and summarize the outstanding questions concerning synthesis of proanthocyanidins from the chemical, biochemical and molecular genetic perspectives.

Proanthocyanidins--a final frontier in flavonoid research?

Proanthocyanidins are oligomeric and polymeric end products of the flavonoid biosynthetic pathway. They are present in the fruits, bark, leaves and seeds of many plants, where they provide protection against predation. At the same time they give flavor and astringency to beverages such as wine, fruit juices and teas, and are increasingly recognized as having beneficial effects on human health. The presence of proanthocyanidins is also a major quality factor for forage crops. The past 2 years have seen important breakthroughs in our understanding of the biosynthesis of the building blocks of proanthocyanidins, the flavan-3-ols (+)-catechin and (-)-epicatechin. However, virtually nothing is known about the ways in which these units are assembled into the corresponding oligomers in vivo. Molecular genetic approaches are leading to an understanding of the regulatory genes that control proanthocyanidin biosynthesis, and this information, together with increased knowledge of the enzymes specific for the pathway, will facilitate the genetic engineering of plants for introduction of value-added nutraceutical and forage quality traits.