Investigating the Antituberculosis Activity of Selected Commercial Essential Oils and Identification of Active Constituents Using a Biochemometrics Approach and In Silico Modeling.

Tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis which has become prevalent due to the emergence of resistant M. tuberculosis strains. The use of essential oils (EOs) as potential anti-infective agents to treat microbial infections, including TB, offers promise due to their long historical use and low adverse effects. The current study aimed to investigate the in vitro anti-TB activity of 85 commercial EOs, and identify compounds responsible for the activity, using a biochemometrics approach. A microdilution assay was used to determine the antimycobacterial activity of the EOs towards some non-pathogenic Mycobacterium strains. In parallel, an Alamar blue assay was used to investigate antimycobacterial activity towards the pathogenic M. tuberculosis strain. Chemical profiling of the EOs was performed using gas chromatography-mass spectrometry (GC-MS) analysis. Biochemometrics filtered out putative biomarkers using orthogonal projections to latent structures discriminant analysis (OPLS-DA). In silico modeling was performed to identify potential therapeutic targets of the active biomarkers. Broad-spectrum antimycobacterial activity was observed for Cinnamomum zeylanicum (bark) (MICs = 1.00, 0.50, 0.25 and 0.008 mg/mL) and Levisticum officinale (MICs = 0.50, 0.5, 0.5 and 0.004 mg/mL) towards M. smegmatis, M. fortuitum, M. gordonae and M. tuberculosis, respectively. Biochemometrics predicted cinnamaldehyde, thymol and eugenol as putative biomarkers. Molecular docking demonstrated that cinnamaldehyde could serve as a scaffold for developing a novel class of antimicrobial compounds by targeting FtsZ and PknB from M. tuberculosis.

Exploring four South African Croton species for potential anti-inflammatory properties: in vitro activity and toxicity risk assessment.

ETHNOPHARMACOLOGICAL RELEVANCE: The African Continent harbours approximately 26 Croton species. Many Croton species are used in traditional medicine in southern Africa to treat a variety of ailments including malaria, tuberculosis, microbial infection and inflammation. Considering the high diversity of the genus Croton, the ethnopharmacological information available on southern African species is rather limited. Furthermore, the potential for novel anti-inflammatory drug scaffolds has not previously been investigated. AIM OF THE STUDY: The aim of the study was to evaluate the potential of four South African Croton species extracts (Croton gratissimus, Croton pseudopulchellus, Croton sylvaticus, and Croton steenkampianus) for anti-inflammatory activity targeting the TLR4 signalling pathway and to assess the potential risk for hepatotoxicity and genotoxicity using an in vitro cellomics approach. MATERIAL AND METHODS: Leaf extracts of C. gratissimus, C. pseudopulchellus, C. sylvaticus and C. steenkampianus were prepared using methanol and chloroform (1:1, v/v). The anti-inflammatory activity was determined using LPS induced nitric oxide production in RAW 264.7 macrophages, while the hepatotoxicity and genotoxicity was evaluated using multi-parameter end point analysis in C3A and Vero cells, respectively. Mitochondrial membrane potential, mitochondrial mass, oxidative stress, lysosomal content and lipid accumulation were used as markers to assess the risk for hepatotoxicity. RESULTS: All four species attenuated nitric oxide production with negligible cytotoxicity. However, C. gratissimus yielded the most favorable profile. Cell density was significantly reduced in both C3A and Vero cells with the C. gratissimus extract providing a suitable toxicity profile amenable to further high content analysis. While there was no meaningful effect on mitochondrial dynamics, a strong dose dependent increase in lipid content, paralleled by an expansion of the lysosomal compartment, identifies a potential risk for steatosis. Risk for genotoxicity was investigated using the micronucleus assay which revealed a dose dependent increase in micronuclei formation. Changes in nuclear morphology and cell ploidy further strengthens the associated risk for genotoxicity and suggests the extract from C. gratissimus may function as an aneugen. Collectively, the data demonstrates that although the selected species possess anti-inflammatory components, the risk for possible hepatotoxic and genotoxic side effects may negate their prospect towards further drug development.

A review of biological activities and phytochemistry of six ethnomedicinally important South African Croton species.

ETHNOPHARMACOLOGICAL RELEVANCE: The genus Croton (Euphorbiaceae) encompasses 1300 species, which consist of a variety of trees and shrubs distributed across the world. About 26 species are harboured on the African continent. This genus plays an essential role in African folk medicine. Croton species are traditionally used for the treatment of many diverse conditions such as diabetes, malaria, sexually transmitted diseases, cancer, inflammation, fever, digestive problems and fungal infections. AIM OF THE REVIEW: To provide a comprehensive overview of the ethnobotany, traditional uses, phytochemistry and biological activities of six selected southern Africa Croton species; C.gratissimus Burch., C. megalobotrys Müll.-Arg., C. menyhartii Gȕrke, C. pseudopulchellus Pax, C. steenkampianus Gerstner and C. sylvaticus Schltdl.). MATERIALS AND METHODS: Various electronic databases, namely Google, Google Scholar, Scopus, ScienceDirect, Biomed Central and Pubmed, were used to search for information related to the traditional uses, chemistry and pharmacology of Croton species. Books were also consulted to collect all pertinent information. RESULTS AND DISCUSSION: The ethnopharmacology, phytochemistry and biological activities of southern African Croton species are reviewed. The literature revealed that Croton species are trusted traditional medicines for the treatment of microbial infections and malaria. The non-volatile components of Croton species include flavonoids, terpenoids and alkaloids, while the volatile constituents comprise mainly of monoterpenes (α-phellandrene, α-pinene and 1,8-cineole) and sesquiterpenes (caryophyllene oxide). Most of the reported biological activities (anti-oxidant, antimicrobial, anticancer and antimalarial) were based on in vitro assays and were accredited to various extracts. However, both in vitro and in vivo studies, linking the reported activities to specific compounds, are still lacking. CONCLUSIONS: Croton species are used in traditional medicine to treat a range of ailments, and various in vitro biological activities have been investigated, with some extracts exhibiting good activity that could be considered for further investigation. The in vitro activities obtained seem to justify the use of Croton species in traditional medicine. Data on in vivo studies are scarce and studies usually focused on a single collection. The need to establish a quality control protocols for the standardisation of these herbal drugs is also important.

Chemotypic variation of non-volatile constituents of Artemisia afra (African wormwood) from South Africa.

Artemisia afra (African wormwood) is a popular medicinal plant of southern Africa and is an excellent candidate for commercialisation. This current study was aimed at exploring the phytochemistry and chemical variation of non-volatile compounds within wild populations of A. afra, and developing chromatographic quality control protocols for raw materials based on the identification of marker compounds. Chromatographic data, from samples representing 12 distinct populations, were obtained using liquid chromatography-mass spectrometry. An untargeted chemometric approach revealed three clusters. Marker compounds for each cluster, revealed through discriminant analysis, were isolated and identified using NMR spectroscopy, as acacetin (1) (Group 1), chrysoeriol (2) (Group 2), and 3,5-di-O-caffeoylquinic acid (3) and scopoletin (4) (Group 3). In addition, (3) and rutin (5), (both reported for the first time from A. afra), and (1), (2), (4) and 4-caffeoylquinic acid (6) were established as reliable markers for species identification, since they were abundant in most samples. Quantitative analysis using a validated method established (4) as the dominant compound in the samples (1080-19,600 µg/g dry weight (d.w.)), followed by (5) (49.5-2490 µg/g d.w.). A high performance thin layer chromatography (HPTLC) method was developed. The Rf values and colours of the bands corresponding to the marker compounds were recorded so that these compounds could be easily identified for quality control purposes. Multivariate analysis of the data using the rTLC online application confirmed the presence of different chemical groupings within the samples. It was deduced that quantitative, rather than qualitative differences, characterised the samples. Future research should focus on comparing the efficacy of the various chemical clusters in multi-target biological assays aligned to the traditional use of the plant.

Beauty in Baobab: a pilot study of the safety and efficacy of Adansonia digitata seed oil

ABSTRACT Recently there has been a renewed impetus in the search for novel ingredients to be used in the cosmetic industry and Baobab (Adansonia digitata L., Malvaceae) seed oil has received high interest. In this study, a commercial Baobab seed oil sample was characterised (fatty acid content) using GCxGC-ToF-MS and a pilot study on the safety and efficacy of the seed oil was performed. The safety and efficacy of Baobab seed oil after topical application was determined using healthy adult female caucasian participants (n = 20). A 2× magnifying lamp was used for visual analysis, while for monitoring and evaluation of the irritancy level, transepidermal water loss (TEWL) and hydration level of the skin, Chromameter®, Aquaflux® and Corneometer® instruments, respectively, were used. In addition, Aquaflux® and Corneometer® instruments were used to assess occlusive effects. Thirteen methyl esters were identified using GCxGC-ToF-MS. The major fatty acids included 36.0% linoleic acid, 25.1% oleic acid and 28.8% palmitic acid with 10.1% constituting trace fatty acids. The irritancy of sodium lauryl sulphate (SLS) in the patch test differed significantly compared to both de-ionised water (p < 0.001) and Baobab seed oil (p < 0.001) but the difference between the irritancy of Baobab seed oil and de-ionised water was not significant (p = 0.850). The moisture efficacy test indicated a reduced TEWL (p = 0.048) and an improved capacitance moisture retention (p < 0.001) for all the test products (Baobab oil, liquid paraffin, Vaseline® intensive care lotion and Vaseline®). The occlusivity wipe-off test indicated an increased moisture hydration (p < 0.001) and decreased TEWL particularly when Baobab oil was applied. Baobab possesses hydrating, moisturising and occlusive properties when topically applied to the skin. Baobab seed oil could be a valuable functional ingredient for cosmeceutical applications.

Menthol: a simple monoterpene with remarkable biological properties.

Menthol is a cyclic monoterpene alcohol which possesses well-known cooling characteristics and a residual minty smell of the oil remnants from which it was obtained. Because of these attributes it is one of the most important flavouring additives besides vanilla and citrus. Due to this reason it is used in a variety of consumer products ranging from confections such as chocolate and chewing gum to oral-care products such as toothpaste as well as in over-the-counter medicinal products for its cooling and biological effects. Its cooling effects are not exclusive to medicinal use. Approximately one quarter of the cigarettes on the market contain menthol and small amounts of menthol are even included in non-mentholated cigarettes. Natural menthol is isolated exclusively from Mentha canadensis, but can also be synthesised on industrial scale through various processes. Although menthol exists in eight stereoisomeric forms, (-)-menthol from the natural source and synthesised menthol with the same structure is the most preferred isomer. The demand for menthol is high and it was previously estimated that the worldwide use of menthol was 30-32,000 metric tonnes per annum. Menthol is not a predominant compound of the essential oils as it can only be found as a constituent of a limited number of aromatic plants. These plants are known to exhibit biological activity in vitro and in vivo such as antibacterial, antifungal, antipruritic, anticancer and analgesic effects, and are also an effective fumigant. In addition, menthol is one of the most effective terpenes used to enhance the dermal penetration of pharmaceuticals. This review summarises the chemical and biological properties of menthol and highlights its cooling effects and toxicity.

An untargeted metabolomic approach in the chemotaxonomic assessment of two Salvia species as a potential source of α-bisabolol.

α-Bisabolol is a commercially important aroma chemical currently obtained from the Candeia tree (Vanillosmopsis erythropappa). Continuous unsustainable harvesting of the Candeia tree has prompted the urgent need to identify alternative crops as a source of this commercially important sesquiterpene alcohol. A chemotaxonomic assessment of two Salvia species indigenous to South Africa is presented and recommended as a potential source of α-bisabolol. The essential oil obtained by hydrodistillation of the aerial parts was analysed by gas chromatography coupled to mass spectrometry (GC-MS) and mid-infrared spectroscopy (MIRS). Orthogonal projections to latent structures-discriminant analysis (OPLS-DA) were used for multivariate classification of the oils based on GC-MS and MIRS data. Partial least squares (PLS) calibration models were developed on the MIRS data for the quantification of α-bisabolol using GC-MS as the reference method. A clear distinction between Salvia stenophylla and Salvia runcinata oils was observed using OPLS-DA on both GC-MS and MIRS data. The MIR calibration model showed high coefficient of determination (R² = 0.999) and low error of prediction (RMSEP=0.540%) for α-bisabolol content.

Eugenol--from the remote Maluku Islands to the international market place: a review of a remarkable and versatile molecule.

Eugenol is a major volatile constituent of clove essential oil obtained through hydrodistillation of mainly Eugenia caryophyllata (=Syzygium aromaticum) buds and leaves. It is a remarkably versatile molecule incorporated as a functional ingredient in numerous products and has found application in the pharmaceutical, agricultural, fragrance, flavour, cosmetic and various other industries. Its vast range of pharmacological activities has been well-researched and includes antimicrobial, anti-inflammatory, analgesic, anti-oxidant and anticancer activities, amongst others. In addition, it is widely used in agricultural applications to protect foods from micro-organisms during storage, which might have an effect on human health, and as a pesticide and fumigant. As a functional ingredient, it is included in many dental preparations and it has also been shown to enhance skin permeation of various drugs. Eugenol is considered safe as a food additive but due to the wide range of different applications, extensive use and availability of clove oil, it is pertinent to discuss the general toxicity with special reference to contact dermatitis. This review summarises the pharmacological, agricultural and other applications of eugenol with specific emphasis on mechanism of action as well as toxicity data.

Constituents of cinnamon inhibit bacterial acetyl CoA carboxylase.

Cinnamon bark ( CINNAMOMUM ZEYLANICUM) is used extensively as an antimicrobial material and currently is being increasingly used in Europe by people with type II diabetes to control their glucose levels. In this paper we describe the action of cinnamon oil, its major component, TRANS-cinnamaldehyde, and an analogue, 4-hydroxy-3-methoxy- TRANS-cinnamaldehyde against bacterial acetyl-CoA carboxylase in an attempt to elucidate the mechanism of action of this well-known antimicrobial material. These natural products inhibited the carboxyltransferase component of ESCHERICHIA COLI acetyl-CoA carboxylase but had no effect on the activity of the biotin carboxylase component. The inhibition patterns indicated that these products bound to the biotin binding site of carboxyltransferase with TRANS-cinnamaldehyde having a K (i) value of 3.8 ± 0.6 mM. The inhibition of carboxyltransferase by 4-hydroxy-3-methoxy- TRANS-cinnamaldehyde was analyzed with a new assay for this enzyme based on capillary electrophoresis. These results explain, in part, the antibacterial activity of this well-known antimicrobial material.