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Author: search.filters.author.Singh, Alveera

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    Antimycobacterial, docking and molecular dynamic studies of pentacyclic triterpenes from Buddleja saligna leaves
    (Taylor and Fancis Online, 2017) Singh, Alveera; Venugopala, Katharigatta Narayanaswamy; Khedr, Mohammed A.; Pillay, Mellendran; Nwaeze, Kenneth U.; Coovadia, Yacoob; Shode, Francis; Odhav, Bharti
    Buddleja saligna (family Buddlejaceae) is a medicinal plant endemic to South Africa. Two isomeric pentacyclic triterpenes, oleanolic acid and ursolic acid, were isolated from the leaves of B. saligna using silica gel column chromatography. Compounds oleanolic acid and ursolic acid were subjected to derivatization with acetic anhydride in the presence of pyridine to obtain oleanolic acid-3-acetate and ursolic acid-3-acetate, respectively. The structures of these compounds were fully characterized by detailed nuclear magnetic resonance (NMR) investigations, which included 1H and 13C NMR. Molecular docking studies predicted the free binding energy of the four triterpenes inside the steroid binding pocket of Mycobacterium tuberculosis fadA5 thiolase compared to a reported inhibitor. Thus, their ability to inhibit the growth of M. tuberculosis was predicted and was confirmed to possess significant antimycobacterial activity when tested against Mycobacterium smegmatis, M. tuberculosis H37Rv (ATCC 25177), clinical isolates of multi-drug-resistant M. tuberculosis (MDR-TB) and extensively drug-resistant M. tuberculosis (XDR-TB) using the Micro Alamar Blue Assay. Ursolic acid was isolated from this plant for the first time.
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    Bioactive compounds from South African plants against Mycobacterium tuberculosis
    (2016) Singh, Alveera; Odhav, Bharti; Coovadia, Yacoob
    Mycobacterium tuberculosis (MTB), the causative agent of tuberculosis (TB) has infected approximately one-third of the world population, with 9.6 million TB cases in 2014. The emergence of multi-drug resistant (MDR) and extensively-drug resistant (XDR) strains of MTB has further complicated the problem of TB control. It is now imperative that novel antimycobacterial compounds are discovered in order to treat infections and reduce the duration of current TB therapy courses. For centuries, medicinal plants have been used globally worldwide for the treatment and prevention of various ailments. This occurs particularly in developing countries where infectious diseases are endemic and modern health facilities and services are inadequate. In recent years, the use and search for plant drug derivatives have been fast-tracked. Ethnopharmacologists, botanists, microbiologists, and natural product chemists are trying to discover phytochemicals which could be developed for the treatment of infectious diseases, especially TB. Plants are rich in a wide variety of secondary metabolites, such as tannins, terpenoids, alkaloids, and flavonoids, which have been found in vitro to have antimycobacterial activity. In the search for new lead compounds, nine medicinal plant species, Buddleja saligna, Capparis tomentosa, Carpobrotus dimidiatus, Dichrostachys cinerea, Ekerbergia capensis, Ficus Sur, Gunnera perpensa, Leonotis leonurus and Tetradenia riparia were collected in Kwa-Zulu Natal (KZN) following report of their therapeutic use in traditional medicine to treat symptoms and infections related to TB. They were tested in vitro for their activity against Mycobacterium smegmatis, Mycobacterium tuberculosis H37Rv (ATCC 25177) and three well-characterized clinical isolates of MDR-TB and XDR-TB using the agar incorporation method. The minimum inhibitory concentration of the active plant extracts was determined using the broth microdilution method. Our findings show that five of the nine plants screened have antimycobacterial activity with concentrations ranging from 125 µg/ml to 1000 µg/ml. The aqueous extracts of G. perpensa and T. riparia; and the methanolic extracts of B. saligna, C. tomentosa, and C. dimidiatus possessed significant activity against M. smegmatis, M. tuberculosis H37Rv (ATCC 25177) and the three well-characterized clinical isolates of MDR-TB and XDR-TB. The cytotoxic effect of the active plant extracts was evaluated against the mouse BALB/C monocyte-macrophage (J774.2) and peripheral blood mononuclear cells (PBMCs). The toxic effects of the active plant extracts were evaluated using the brine shrimp lethality assay. Except for a high concentration of G. perpensa none of the other plants which possessed antimycobacterial activity showed any toxic or cytotoxic activity. The active plant extracts were thereafter assessed to determine if they had any effect on the survival or death of mycobacterial species, M. smegmatis, bound within the macrophage (J774.2) cell line at a concentration of 100 µg/ml. B. saligna had inactivated most of the phagocytosed bacilli after 24 hours of treatment therefore, it has a bactericidal effect on the mycobacteria located within the mouse macrophage. A phytochemical investigation of the leaves of B. saligna led to the isolation of two isomeric pentacyclic triterpene compounds namely Oleanolic Acid (OA) and Ursolic Acid (UA) using thin layer chromatography followed by silica gel column chromatography. The structures of these compounds were fully characterized by detailed NMR investigations, which included 1H and 13C NMR. Ursolic acid was isolated from this plant for the first time. Two-dimensional (2D) and three-dimensional (3D) quantitative structure-activity relationship (QSAR) studies were carried out to provide insight on the interaction of the compounds with the enzyme. Molecular docking studies predicted the free binding energy of the triterpenes inside the steroid binding pocket of Mycobacterium tuberculosis fadA5 thiolase compared to a reported inhibitor. Thus, their ability to inhibit the growth of Mycobacterium tuberculosis was predicted and was confirmed to possess significant antimycobacterial activity when tested against M. smegmatis, M. tuberculosis H37Rv (ATCC 25177), clinical isolates of MDR-TB and XDR-TB using the Microplate Alamar Blue Plate (MABA) assay. The present study has scientifically validated the traditional use of medicinal plant B. saligna.
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    The antimosquito properties of extracts from flowering plants in South Africa
    (NCBI, 2013) Chalannavar, Raju K.; Hurinanthan, Vashka; Singh, Alveera; Venugopala, Katharigatta Narayanaswamy; Gleiser, Raquel M.; Baijnath, Himansu; Odhav, Bharti
    Extracts of selected flowering plants, which are considered eco-friendly, are used for the treatment of numerous ailments and vector control worldwide. This has resulted in approximately 25 per cent of currently used drugs being derived from herbal sources. The aqueous and methanolic extracts of twelve plant species, Psidium guajava (pink fruit), Psidium guajava (white fruit), Psidium cattleianum var. cattleianum, Psidium guineense and Psidium X durbanensis, Achyranthes aspera, Alternanthera sessilis, Guilleminea densa, Capparis tomentosa, Leonotis leonurus, Dichrostachys cinerea and Carpobrotus dimidiatus, were tested for insecticidal activity, including larvicidal, adulticidal and repellent activities against the adult female mosquito, Anopheles arabiensis. The extracts of P. guajava (white fruit), C. tomentosa, L. leonurus,D. cinerea, and C. dimidiatus exerted a pronounced inhibitory effect on adult insects, while those of P. guajava (pink fruit), P. X durbanensis, P. cattleianum var. cattleianum, P. guineense, A. aspera, A. sessilis, and G. densa were ineffective and failed to satisfy the criteria set by the World Health Organization. In the tests for repellency against An. arabiensis, all the tested aqueous and methanolic plant extracts except those of A. sessilis repelled 80-100% of mosquitoes. The most effective mosquito repellents were the methanol and aqueous extracts of P. guajava (pink fruit), P. X durbanensis, P. cattleianum var. cattleianum, P. guineense, G. densa,L. leonurus and D. cinerea, which are potential sources of cost effective mosquito repellents to be utilized in malarial endemic areas.
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    Bioactivity of famine food plants from the family: Amaranthaceae
    (2009) Singh, Alveera; Odhav, Bharti; Reddy, Lalini
    Information regarding the nutritional value of wild food plants in Africa and current information varies from source to source. Prior to commercialization of wild foods the nutritional, ethnobotanical, medical, chemical, anthropological and toxicity requires investigation. Plants from the Amaranthaceae family were chosen because the family is characterized by several species which are used by indigenous communities as a source of nutrition in different plants of the world. The focus of this study was to investigate the nutritional and biological activities of three plants from the Amaranthaceae family viz. Achyranthes aspera, Alternanthera sessilis and Guilleminea densa that are considered famine plants. This study aimed to determine the nutritional value (proximate, minerals and vitamins), biological activity, toxicity and potential of a tissue culture system for three species from the family Amaranthaceae. Nutritional analysis comprised of determining moisture, ash, protein, fat, carbohydrate, dietary fibre and energy. Mineral analysis of calcium, copper, iron, magnesium, manganese, phosphorus, sodium and zinc was performed by microwave digestion and then analyzed by ICP Spectrophotometry. Vitamin A, Vitamin B1, Vitamin B2, Vitamin B3 and Vitamin C were also analyzed. For biological and safety analyses aqueous and methanolic extracts were prepared. Anti-oxidative and anti-inflammatory properties of the extracts were tested; antimicrobial activity was tested by evaluating the bactericidal, fungal effect and minimum inhibitory concentration on selected bacteria and fungi using the agar disk diffusion method. Anti mosquito potential was determined by setting up repellency, larvacidal assay and insecticidal assay. The safety and toxicity analysis was carried out by measuring cytotoxicity, toxicity and mutagenicity. The potential of an in vitro tissue culture system of A. aspera, A. sessilis and G. densa was determined using micropropagation. A. aspera indicated significant amounts moisture, ash, dietary fibre, protein, vitamin B1, vitamin B2, magnesium and manganese. Plant extracts of A. aspera had antibacterial activity against the Gram negative bacteria Esherichia coli, Pseudomas aeroginosa and Salmonella typhi; Gram positive bacteria Staphylococcus epidermis and Staphylococcus aureus. The methanolic extract had antifungal activity against Sacchromyces cerevisiae and exhibited significant free radical scavenging activity as well as 85% repellency against Anopheles arabiensis. The aqueous extract stimulated the growth of the K562 (Chronic Myclogenous Leukaemia) cell line and the plant extracts showed no mutagenicity or toxicity. A. sessilis indicated significant levels of ash, dietary fibre, protein, energy, vitamin A, vitamin B1, vitamin B2, vitamin B3, iron, magnesium and manganese present. Plant extracts of A. sessilis had antibacterial activity against Gram negative bacteria P. aeroginosa and Gram positive bacteria S. epidermis. The plant also showed antifungal activity against the yeasts S. cerevisiae and Candida albicans. The methanolic plant extract showed excellent antioxidant activity. The aqueous plant extract stimulated the growth of the K562 cell line and the plant extracts possessed no mutagenicity or toxicity. This plant grew well in a tissue culture system where it was propagated from callus to a fully grown plant able to survive in environmental conditions. G. densa has ash and dietary fibre, vitamin B2, vitamin B3 and iron. The plant extracts had antibacterial activity against Gram negative bacteria E. coli, P. aeroginosa and Klebsiella. oxytoca; Gram positive bacteria Baccilus stereathermophilus and S. aureus. The plant also has antifungal activity against C. albicans and significant repellency activity against A. arabiensis where it showed 100% repellency. This plant was not found to be mutagenic or toxic. The results obtained from this study show promising potential for the plants to be exploited as famine food plants. The nutritional value, biological activity and ability to micropropagate A. aspera, A. sessilis and G. densa indicates a good potential for purposes of harnessing biotechnological products.