Browsing by Author "Marnewick, Jeanine L."
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Item Acylphloroglucinol derivatives from the South African helichrysum niveum and their biological activities(MDPI, 2015) Popoola, Olugbenga K.; Marnewick, Jeanine L.; Rautenbach, Fanie; Iwuoha, Emmanuel I.; Hussein, Ahmed A.Abstract: Phytochemical investigation of aerial parts of Helichrysum niveum (H. niveum) using different chromatographic methods including semi-preparative HPLC afforded three new (1–3) and six known (4–10) acylphloroglucinols alongside a known dialcohol triterpene (11). The structures of the isolated compounds were characterized accordingly as 1-benzoyl-3 (3-methylbut-2-enylacetate)-phloroglucinol (helinivene A, 1), 1-benzoyl-3 (2S-hydroxyl-3- methylbut-3-enyl)-phloroglucinol (helinivene B, 2), 8- (2-methylpropanone)-3S, 5, 7-trihydroxyl- 2,2-dimethoxychromane (helinivene C, 3), 1-(2-methylbutanone)-4-O-prenyl-phloroglucinol (4), 1-(2-methylpropanone)-4-O-prennyl-phloroglucinol (5), 1-(butanone)-3-prenyl-phloroglucinol (6), 1- (2-methylbutanone)-3-prenyl-phloroglucinol (7), 1-butanone-3- (3-methylbut-2-enylacetate)- phloroglucinol (8), 1-(2-methylpropanone)-3-prenylphloroglucinol (9), caespitate (10), and 3β-24-dihydroxyterexer-14-ene (11). Excellent total antioxidant capacities were demonstrated by helinivenes A and B (1 and 2) when measured as oxygen radicals absorbance capacity (ORAC), ferric-ion reducing antioxidant power (FRAP), trolox equivalent absorbance capacity (TEAC) and including the inhibition of Fe2+-induced lipid peroxidation (IC50 = 5.12 ± 0.90; 3.55 ± 1.92) µg/mL, while anti-tyrosinase activity at IC50 = 35.63 ± 4.67 and 26.72 ± 5.05 µg/mL were also observed for 1 and 2, respectively. This is the first chemical and in vitro biological study on H. niveum. These findings underpin new perspectives for theItem Alpha-glucosidase and alpha-amylase inhibitory activities, molecular docking, and antioxidant capacities of salvia aurita constituents(MPDI, 2020) Etsassala, Ninon G.E.R.; Badmus, Jelili A.; Marnewick, Jeanine L.Diabetes mellitus (DM) is one of the most dangerous metabolic diseases with a high rate of mortality worldwide. It is well known that insulin resistance and deficiency in insulin production from pancreatic β-cells are the main characteristics of DM. Due to the detrimental side effects of the current treatment, there is a considerable need to develop new effective antidiabetic drugs, especially alpha-glucosidase and alpha-amylase inhibitors with lesser adverse effects. These inhibitors are known to be directly involved in the delay of carbohydrate digestion, resulting in a reduction of glucose absorption rate and, consequently, reducing the postprandial rise of plasma glucose, which can reduce the risk of long-term diabetes complications. Furthermore, natural products are well-known sources for the discovery of new bioactive compounds that can serve as scaffolds for drug discovery, including that of new antidiabetic drugs. The phytochemical investigation of Salvia aurita collected from Hogobach Pass, Eastern Cape Province, South Africa (SA), yielded four known abietane diterpenes namely carnosol (1), rosmanol (2), 7-methoxyrosmanol (3), 12-methoxycarnosic acid (4), and one flavonoid named 4,7-dimethylapigenin (5)Item Biosynthesis, Characterization, and Biological Activities of Procyanidin Capped Silver Nanoparticles(Multidisciplinary Digital Publishing Institute, 2020-09-19) Badeggi, Umar M.; Badmus, Jelili A.; Botha, Subelia S.; Ismail, Enas; Marnewick, Jeanine L.; Africa, Charlene Wilma Joyce; Hussein, Ahmed A.In this study, procyanidin dimers and Leucosidea sericea total extract (LSTE) were employed in the synthesis of silver nanoparticles (AgNPs) and characterized by ultraviolet-visible (UV-Visible) spectroscopy, high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), and dynamic light scattering (DLS) techniques. AgNPs of about 2-7 nm were obtained. DLS and stability evaluations confirmed that the AgNPs/procyanidins conjugates were stable. The formed nanoparticles exhibited good inhibitory activities against the two enzymes studied. The IC50 values against the amylase enzyme were 14.92 ± 1.0, 13.24 ± 0.2, and 19.13 ± 0.8 µg/mL for AgNPs coordinated with LSTE, F1, and F2, respectively. The corresponding values for the glucosidase enzyme were 21.48 ± 0.9, 18.76 ± 1.0, and 8.75 ± 0.7 µg/mL. The antioxidant activities were comparable to those of the intact fractions. The AgNPs also demonstrated bacterial inhibitory activities against six bacterial species. While the minimum inhibitory concentrations (MIC) of F1-AgNPs against Pseudomonas aeruginosa and Staphylococcus aureus were 31.25 and 15.63 µg/mL respectively, those of LSTE-AgNPs and F2-AgNPs against these organisms were both 62.50 µg/mL. The F1-AgNPs demonstrated a better bactericidal effect and may be useful in food packaging. This research also showed the involvement of the procyanidins as reducing and capping agents in the formation of stable AgNPs with potential biological applications.Item The chemical and biological characterization of South African helichrysum species(University of the Western Cape, 2015) Popoola, Olugbenga Kayode; Mohammed, Ahmed; Marnewick, Jeanine L.South Africa has immensely rich natural flora diversity with more than 20 000 species of higherplants. Asteraceae is one of the biggest families of flowering plants with about 246 genera and 2,300 species in southern Africa. South Africa being home to more than 35 % of the world's Helichrysum species (c.a. 244) of which many are used in traditional medicine, and can be considered as a potential resource for new bioactive chemical entities. Chemical studies on the total extract of the South African Helichrysum species viz: H. teretifolium, H. niveum and H. rutilans resulted in the isolation of twenty eight [14 flavonoids (C1-C10; C22- C25), 10 phloroglucinols (C11-C20) and 4 terpenoids (C21, C26-C28)] pure compounds. The chemical structures of the newly isolated compounds were elucidated on the basis of their 1D and 2D-NMR, HRMS, IR and UV spectroscopic data as heliteretifolin (C1), 1-benzoyl-3-(3-methyl- 2-butenylacetate)-phloroglucinol (helinivene A, C11), 1-benzoyl-3-(2-hydroxyl-3-methyl-3- butene-1-yl)-phloroglucinol (helinivene B, C12) and 8-(2-methyl-1-propanone)-3,5,7- trihydroxyl-2,2-dimethoxychromone (helinivene C, C13), while occurrence of 7- methoxyisoglabranin (C6), 4-methoxyquercetin (C8), 4`-methoxykaempferol (C9), mosloflavone (C10), 3β-24-dihydroxyterexer-14-ene (C21), 5,7,8-trihydroxy-3,6-dimethoxyflavone-8-O-2- methyl-2-butanoate (C22) and 15--hydroxy-(-)-kaur-16-en-19-oic acid (C28), from Helichrysum genus were reported for the first time. In vitro inhibition of oxidative stress by the isolated compounds were measured as total antioxidant capacity using the FRAP, TEAC, ORAC (hydroxyl and peroxyl radicals) as well as Fe2+-induced microsomal lipid peroxidation assays. Inhibitory activities against skin-diseases related enzymeswere evaluated in a tyrosinase and elastase non-biological system, while In vitro prooxidant behavior of the compounds was also investigated in the presence of copper (II). Compounds C7, C8, C11 and C12 in comparison with the commercial antioxidant EGCG demonstrated TEAC (4529.01 ± 2.44; 4170.66 ± 6.72; 19545.00 ± 10.25; 43615.73 ± 6.66; vs 11545.40 ± 17.28) μM TE/g respectively, and ORAChydroxyl radical (7.265 ± 0.71; 6.779 ± 3.40; 64.85± 10.95; 94.97 ± 5.80; vs 3.91 ± 4.65) X106 μM TE/g capacities, respectively. Inhibition of Fe2+- induced microsomal lipid peroxidation demonstrated by C7, C8, C11 and C12 expressed as IC50 values included: 2.931 ± 0.64; 6.449 ± 3.16; 5.115 ± 0.90; 3.553 ± 1.92 µg/mL respectively. Additionally, the total antioxidant capacities measured as FRAP (4816.31 ± 7.42; 3584.17 ± 0.54)µMAAE/g, and ORACperoxyl radical (17.836 ± 2.90; 12.545 ± 5.07) X 103 µMTE/g were also observed for compounds C7 & C8, respectively. Compound C7 demonstrated potent anti-tyrosinase activity with IC50 8.092 ± 7.14, while mild anti-tyrosinase activities were demonstrated by compounds C8, C11, C12, C22 and C23 and expressed as IC50 values (IC50 = 27.573 ± 3.11; 35.625 ± 4.67; 26.719 ± 5.05; 25.735 ± 9.62;24.062 ± 0.61) µg/mL respectively. Anti-elastase activity with IC50 values of 25.313 ± 7.85 µg/mL was observed for C13. This is the first scientific report to be carried out on the chemical and biological profiles of H. teretifolium.H. niveum and H. rutilans. The results suggest that these isolated compounds might become natural agents to inhibit oxidative stress and skin disease-related enzymes, with the prospect of being utilized in cosmetic products formulation upon further biological and clinicalinvestigations.Item Inhibition of oxidative stress and skin aging-related enzymes by prenylated chalcones and other flavonoids from helichrysum teretifolium(MDPI, 2015) Popoola, Olugbenga K.; Marnewick, Jeanine L.; Rautenbach, Fanie; Ameer, Farouk; Iwuoha, Emmanuel I.; Hussein, Ahmed A.Ten flavonoid-related structures viz. heliteretifolin (1), isoxanthohumol (2), 2',4',6'-trihydroxy-3'-prenylchalcone (3), isoglabranin (4), glabranin (5), 7-methoxyisoglabranin (6), quercetin (7), 4'-methoxyquercetin (8), 4'-methoxykaempferol (9) and mosloflavone (10) were isolated from a H. teretifolium methanolic extract and identified. One of them (compound 1) is reported for the first time from a natural source, while compounds 6, 8–10 were isolated for the first time from the genus Helichrysum. The total extract of H. teretifolium showed potent antioxidant activity. When tested for total antioxidant capacity compound 3 possesses moderate biological activity compared to 2, which displayed some of the highest TEAC values (4529.01 ± 2.44; 4170.66 ± 6.72) µM TE/g, respectively. Compounds 7 and 8 demonstrated the highest inhibitory activities on Fe2+-induced lipid peroxidation (IC50 = 2.931; 6.449 µg/mL); tyrosinase (8.092; 27.573) and elastase (43.342; 86.548). Additionally, the total antioxidant capacities measured as FRAP (4816.31 ± 7.42; 3584.17 ± 0.54) µM AAE/g, and ORAC for hydroxyl radical (7.265 ± 0.71; 6.779 ± 3.40) × 106 and peroxyl radical (17.836 ± 2.90; 12.545 ± 5.07) × 103 µM TE/g were also observed for compounds 7 and 8, respectively. In conclusion, H. teretifolium total extract represents a rich source of bioactive constituents with potent antioxidant and moderate anti-tyrosinase and anti-elastase activities that can help to avert accumulation of free radicals in the body, and could therefore be good candidates for the prevention and/or treatment of skin-related conditions, such as aging. This is the first scientific report on the chemical and biological profile of H. teretifolium.Item Nitrogen and carbon costs of growth and antioxidant production during acclimation to environmental stress in two species of gethyllis(University of the Western Cape, 2012) Daniëls, Christiaan Winston; Mabusela, Wilfred Thozamile; Valentine, Alexander J.; Marnewick, Jeanine L.Gethyllis multifolia L. Bolus and G. villosa Thunb. are winter-growing, summerblooming,deciduous and bulbous geophytes that grow naturally in the semi-arid succulent Karoo biome of South Africa. Both species grow under full sun conditions and have four distinctive growth phases: a winter (cold and wet) growing phase, leaf senescence phase towards spring, flowering phase during the hot and dry summer months, and fruit and leaf formation phase in autumn. The medicinal uses of this genus (including G. multifolia “Kukumakranka” and G.villosa “hairy kukumakranka”) range from cures for colic, digestive disturbances,teething problems, fatigue, boils, bruises and insect bites, to being used as an aphrodisiac. Gethyllis multifolia is threatened in its natural habitat and is listed in the ‘Vulnerable’ category of the ‘Red Data List of Southern African Plants’ and the ‘IUCN-World Conservation Union List of Plants’. The literature indicate that the habitats of both species are being exposed to drier conditions and is further threatened by the encroachment of invasive indigenous plant species. It is not known to which extent these factors may pose a threat to the existence of both species. The first objective of this investigation was to determine the costs of vegetative and reproductive growth during the seasonal life cycle of the plant, using carbon(C) and nitrogen (N) as a physiological currency. The second objective was to elucidate a functional basis to explain the difference in the conservation status of both species in their natural habitat. Both species were subjected to drought and shading as environmental stresses and the plant physiological performance was investigated via photosynthetic gas exchange. The third objective of the study was to evaluate the antioxidant content (total polyphenol, flavonol/flavone and flavanone content) and antioxidant capacity [ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC) and 2,2'-azino-di-3-ethylbenzthiazoline sulphonate (ABTS) radical cation scavenging ability] of natural populations and plant samples that were exposed to photo-and-drought environmental stresses. This study was done to elucidate the antioxidant profile of plant parts of natural populations as well as providing farmers, traditional healers and pharmaceutical companies with cultivation environmental conditions to enhance the antioxidant properties of the species. This investigation also attempted to isolate and characterize, by means of thin-layer chromatography (TLC) and column chromatography (CC), natural compounds from both species to lend support to the purported antioxidant benefit of both species and to further lend support to claims made by traditional healers of the medicinal potential of the genus. This study, however, did not engage in any in vivo studies or human trials to support published literature of the medicinal benefits of the genus.Item Photosynthetic adaptation of two semi-arid species of Gethyllis (Kukumakranka) to drought-and-shade stress(Elsevier, 2013) Daniels, C.W.; Mabusela, Wilfred T.; Marnewick, Jeanine L.; Valentine, A.J.Gethyllis multifolia and Gethyllis villosa are winter-growing, summer-blooming, deciduous and bulbous geophytes that grow naturally in the semi-arid ‘Succulent Karoo Biome’ of South Africa. G. multifolia is threatened in its natural habitat and resides in the ‘Vulnerable’ category of the ‘Red Data List of Southern African Plants’. Previous investigations suggested that G. multifolia is more sensitive to drought stress than G. villosa and that both species adopted certain morphological changes in their leaves during shade stress. Current models indicate that this biome is being exposed to increasingly drier conditions and shading from encroaching indigenous plant species. In this study, the photosynthetic gas exchange responses of both species to drought and shade stresses were investigated and the ‘Vulnerable’ conservation status of G. multifolia. This investigation found that during drought stress G. villosa had a more enhanced photosynthetic performance than G. multifolia which appears not to be related to foliar adaptations such as specific leaf mass (SLM), but to the G. villosa's leaves maintaining their stomatal conductance (Gs), photosynthetic light compensation (LCP) and photon yields. Furthermore, during shade stress G. villosa also had an improved photosynthetic performance by not altering its photosynthetic LCP during reduced light conditions. It can be concluded that G. multifolia has a lower capacity than G. villosa to adapt its photosynthetic apparatus to changing environments such as increasing drought and shaded conditions. This may be a contributing factor to the threatened conservation status of G. multifolia.