New 21-nordammarane saponins with anti-inflammatory and cytotoxic activities from Lavigeria macrocarpa Oliv.

Chemical investigation of the ethanol extract from the stems and roots of the medicinal plant Lavigeria macrocarpa led to the isolation and structure elucidation of three previously unreported 21-nordammarane-type saponins namely 6α,27-dihydroxy-3,20-dioxo-21-nordammar-24-(Z)-ene 27-O-[α-L-rhamnopyranosyl-(1→2)-ß-D-glucopyranoside] (1), 6α,27-dihydroxy-3-oxo-21-nordammar-24-(Z)-ene 27-O-ß-D-glucopyranoside (2), and 2α,3ß,6α,27-tetrahydroxy-21-nordammar-24-(Z)-ene 27-O-ß-D-glucopyranoside (3) trivially named lavigemacrocarposide A-C, along with eight known secondary metabolites. Acid hydrolysis of lavigemacrocarposide A yielded a new prosapogenin namely 6α,27-dihydroxy-3,20-dioxo-21-nordammar-24-(Z)-ene 27-O-ß-D-glucopyranoside (1a) and the previously unreported artefactual aglycones 1b and 1c. Their structures were elucidated by spectroscopic analyses including mass spectrometry, 1D and 2D NMR as well as chemical evidence. The EtOH extract, some isolated compounds as well as the prosapogenin (1a) and compounds 1b and 1c were evaluated for anti-inflammatory and cytotoxic activity. Icacine (5) exhibited a significant cytotoxicity against both HeLa and MCF-7 cell lines with an IC50 value of 0.78 µg/mL. All the tested compounds showed more that 50% inhibition of NO production, except for 1 and 2.

Lichens: An update on their ethnopharmacological uses and potential as sources of drug leads.

ETHNOPHARMACOLOGICAL RELEVANCE: Lichens, a unique symbiotic association between an alga/cyanobacterium and a fungus, produce secondary metabolites that are a promising source of novel drug leads. The beauty and importance of lichens have not been adequately explored despite their manifold biological activities such as anticancer, antimicrobial, antioxidant, anti-inflammatory, analgesic, antipyretic and antiparasitic. AIM OF THE STUDY: The present review collates and discusses the available knowledge on secondary metabolites and biological activities of lichens (in vitro and in vivo). MATERIALS AND METHODS: Using relevant keywords (lichens, secondary metabolites, bioactivity, pharmacological activities), five electronic databases, namely ScienceDirect, PubMed, Google Scholar, Scopus and Recent Literature on Lichens, were searched for past and current scientific contributions up until May 2022. Literature focusing broadly on the bioactivity of lichens including their secondary metabolites were identified and summarized. RESULTS: A total of 50 review articles and 189 research articles were searched. Information related to antioxidant, antimicrobial, anti-inflammatory, anticancer and insecticidal activities of 90 lichen species (from 13 families) and 12 isolated metabolites are reported. Over 90% of the studies comprised in vitro investigations, such as bioassays evaluating radical scavenging properties, lipid peroxidation inhibition and reducing power, cytotoxicity and antimicrobial bioassays of lichen species and constituents. In vivo studies were scarce and available only in fish and rats. Most of the studies were done by research groups in Brazil, France, Serbia, India and Turkey. There were relatively few reports from Asia and Africa despite the ubiquitous nature of lichens and the high occurrence in these continents. CONCLUSION: Secondary metabolites from lichens are worthy of further investigation in terms of their potential therapeutic applicability, including better understanding of their mechanism(s) of action. This would be of great importance in the search for novel drugs.

Isolation and characterization of the compounds responsible for the antimutagenic activity of Combretum microphyllum (Combretaceae) leaf extracts.

BACKGROUND: Mutations play a major role in the pathogenesis and development of several chronic degenerative diseases including cancer. It follows, therefore that antimutagenic compound may inhibit the pathological process resulting from exposure to mutagens. Investigation of the antimutagenic potential of traditional medicinal plants and compounds isolated from plant extracts provides one of the tools that can be used to identify compounds with potential cancer chemopreventive properties. The aim of this study was to isolate and characterise the compounds responsible for the antimutagenic activity of Combretum microphyllum. METHODS: The methanol leaf extract of C. microphyllum was evaluated for antimutagenicity in the Ames/microsome assay using Salmonella typhimurium TA98. TA100 and TA102. Solvent-solvent fractionation was used to partition the extracts and by using bioassay-guided fractionation, three compounds were isolated. The antimutagenic activity of the three compounds were determined in the Ames test using Salmonella typhimurium TA98, TA100 and TA102. The antioxidant activity of the three compounds were determined by the quantitative 2,2-diphenyl-1-picrylhydrazyl (DPPH)-free radical scavenging method. The cytotoxicity was determined in the MTT assay using human hepatocytes. RESULTS: A bioassay-guided fractionation of the crude extracts for antimutagenic activity led to the isolation of three compounds; n-tetracosanol, eicosanoic acid and arjunolic acid. Arjunolic acid was the most active in all three tested strains with a antimutagenicity of 42 ± 9.6%, 36 ± 1.5% and 44 ± 0.18% in S. typhimurium TA98, TA100 and TA102 respectively at the highest concentration (500 µg/ml) tested, followed by eicosanoic acid and n-tetracosanol. The antioxidant activity of the compounds were determined using the quantitative 2,2 diphenyl-1-picryhydrazyl (DPPH)-free radical scavenging method. Only arjunolic acid had pronounced antioxidant activity (measured as DPPH-free scavenging activity) with an EC50 value of 0.51 µg/ml. The cytotoxicity of the isolated compounds were determined in the MTT assay using human hepatocytes. The compounds had low cytotoxicity at the highest concentration tested with LC50 values >200 µg/ml for n-tetracosanol and eicosanoic acid and 106.39 µg/ml for arjunolic acid. CONCLUSIONS: Based on findings from this study, compounds in leaf extracts of C. microphyllum protected against 4-NQO and MMC induced mutations as evident in the Ames test. The antimutagenic activity of arjunolic acid may, at least in part, be attributed to its antioxidant activity resulting in the detoxification of reactive oxygen species produced during mutagenesis.

Phytochemical analysis with free radical scavenging, nitric oxide inhibition and antiproliferative activity of Sarcocephalus pobeguinii extracts.

BACKGROUND: Free radicals have been implicated in the pathogenesis of diverse metabolic disorders including cancer. Therefore, fighting against free radicals has become an important strategy in the prevention or treatment of such diseases, in addition to direct or indirect anticancer chemotherapy. Sarcocephalus pobeguinii has been used traditionally to treat various diseases in which excess production of free radicals is implicated, warranting investigation of its free radical scavenging, anticancer and anti-inflammatory activity. METHODS: In the present study, extracts from leaves, fruits, roots and bark of Sarcocephalus pobeguinii were evaluated on four human cancer cell lines (MCF-7, HeLa, Caco-2 and A549 cells) and a non-cancerous cell line for their antiproliferative potential. The cells were incubated with the plant extracts for 48 h at 37 °C in a 5% CO2 humidified environment and their cytotoxic effect was determined using the tetrazolium-based colorimetric (MTT) assay. The radical inhibition was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and the 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) scavenging techniques. The nitric oxide inhibitory activity was determined using LPS-activated RAW 264.7 macrophages. The correlation between radical scavenging capacity and antiproliferative activity was also analysed. RESULTS: The extract from leaves of Sarcocephalus pobeguinii (LSP) exhibited the highest cytotoxic effect on all four of the human cancer cell lines but with some cytotoxicity to the normal Vero cells. However, the LSP extract had the best selectivity index, ranging from 3.15 to 18.28. Also, antioxidant and anti-inflammatory assays indicated that the LSP extract had the highest radical scavenging capacity of all the extracts. A positive linear correlation was found between free radical scavenging ability and antiproliferative activity against the four cancer cell lines, with the highest correlation factor (R2 = 0.9914) obtained between DPPH inhibition and antiproliferative activity against A549 cells. CONCLUSIONS: The high selectivity index of the Sarcocephalus pobeguinii leaf extract indicates the potential of using this extract in cancer therapy. Furthermore, the positive correlation between free radical scavenging and antiproliferative activity suggests that the radical scavenging capacity of extracts may contribute to a prediction of their anticancer property.

The antibacterial activity of extracts of nine plant species with good activity against Escherichia coli against five other bacteria and cytotoxicity of extracts.

BACKGROUND: The development of antibiotic resistant bacteria stems from a number of factors, including inappropriate use of antibiotics in human and animal health and their prolonged use as growth promoters at sub-clinical doses in poultry and livestock production. We were interested in investigating plants that could be useful in protecting humans or animals against diarrhoea. We decided to work on extracts of nine plant species with good activity against Escherichia coli based on earlier work in the Phytomedicine Programme. Leaves of nine medicinal plant species with high antibacterial activity against Escherichia coli were extracted with acetone and their minimal inhibitory concentration (MIC) values determined using a microplate serial dilution technique against Gram-positive (Staphylococcus aureus, Enterococcus faecalis and Bacillus cereus) and Gram-negative (Escherichia coli, Salmonella Typhimurium and Pseudomonas aeruginosa) bacteria. Bioautography was used to determine the number of bioactive compounds in each extract. In vitro safety of the extracts was determined using the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide reduction assay on Vero cells. RESULTS: The extracts were active against all the pathogens with average MICs ranging from 0.02 to 0.52 mg/ml. As expected E. coli was relatively sensitive, while E. faecalis and S. Typhimurium were more resistant to the extracts (average MICs of 0.28 mg/ml and 0.22 mg/ml respectively). Cremaspora triflora and Maesa lanceolata leaf extracts had higher activity than the other extracts against Gram-positive and Gram-negative pathogens with mean MICs of 0.07 mg/ml and 0.09 mg/ml respectively. Extracts of Maesa lanceolata and Hypericum roeperianum had the highest total antibacterial activity (TAA) at 1417 and 963 ml/g respectively. All extracts with the exception of that of Maesa lanceolata, Elaeodendron croceum and Calpurnia aurea had relatively low cytotoxicity with LC50 > 20 µg/ml. Cremaspora triflora had the best selectivity index (SI) against S. aureus and E. coli of 2.87 and 1.15 respectively. Hypericum roeperianum had a SI of 1.10 against B. cereus. Bioautography revealed 1-6 visible antimicrobial compounds that were generally non-polar. CONCLUSIONS: There was a weak positive, but statistically non-significant correlation between the potency of the extracts and their cytotoxicity (R = 0.45, ρ > 0.05). The activity of the extracts on the test bacteria was in some cases not correlated with cytotoxicity, as shown by selectivity indices >1. This means that cellular toxicity was probably not due to compounds with antibacterial activity. Some of the extracts had a good potential for therapeutic use against the bacterial pathogens or for application in treating diarhoea. It does not appear that activity against E. coli is a good predictor of activity against Gram-negative rather than Gram-positive bacteria. Further investigation is in progress on C. triflora and H. roeperianum, both of which had promising activities and potential safety based on cytotoxicity.

The correlation between antimutagenic activity and total phenolic content of extracts of 31 plant species with high antioxidant activity.

BACKGROUND: Antimutagenic activity of plant extracts is important in the discovery of new, effective cancer preventing agents. There is increasing evidence that cancer and other mutation-related diseases can be prevented by intake of DNA protective agents. The identification of antimutagenic agents present in plants presents an effective strategy to inhibit pathogenic processes resulting from exposure to mutagenic and/or carcinogenic substances present in the environment. There are no reports on the antimutagenic activities of the plant species investigated in this study. Many mutations related to oxidative stress and DNA damage by reactive oxygen species (ROS) and reactive nitrogen species (RNS) have been identified in numerous human syndromes. Oxidative DNA damage plays a significant role in mutagenesis, cancer, aging and other human pathologies. Since oxidative DNA damage plays a role in the pathogenesis of several chronic degenerative diseases, the decrease of the oxidative stress could be the best possible strategy for prevention of these diseases. Antioxidant compounds can play a preventative role against mutation-related diseases, and thus have potential antimutagenic effects. METHODS: The number of antioxidant compounds present in methanol leaf extracts of 120 plant species was determined using a combination of Thin Layer Chromatography (TLC) and spraying with 2, 2-diphenyl-1-picrylhydrazyl (DPPH). The 31 most promising extracts were selected for further assays. The quantitative antioxidant activity was determined using DPPH free radical scavenging spectrophotometric assay. Total phenolic contents were determined using the Folin-Ciocalteu colorimetric assay. The mutagenicity of 31 selected extracts was determined in the Ames test using Salmonella typhimurium strains TA98 and TA100. The antimutagenicity of the plant extracts against 4-nitroquinoline 1-oxide (4-NQO) was also determined using the Ames test. RESULTS: Of the 120 plant extracts assayed qualitatively, 117 had some antioxidant activity. The selected 31 extracts contained well defined antioxidant compounds. These species had good DPPH free radical antioxidant activity with EC50 values ranging from 1.20 to 19.06 µg/ml. Some of the plant extracts had higher antioxidant activity than L-ascorbic acid (vitamin C). The total phenolic contents ranged from 5.17 to 18.65 mg GAE (gallic acid equivalent)/g plant extract). The total phenolic content of the plant extracts correlated well with the respective antioxidant activity of the plant extracts. No plant extract with good antioxidant activity had mutagenic activity. Several extracts had antimutagenic activity. The percentage inhibition of 4-NQO ranged from 0.8 to 77% in Salmonella typhimurium TA98 and from 0.8 to 99% in strain TA100. There was a direct correlation between the presence of antioxidant activity and antimutagenic activity of the plant extracts. Although no plant extract had mutagenic activity on its own, some of the plant extracts enhanced the mutagenicity of 4-NQO, a phenomenon referred to as comutagenicity. CONCLUSIONS: Some of the plant extracts investigated in this study had potential antimutagenic activities. The antimutagenic activities may be associated with the presence of antioxidant polyphenols in the extracts. From the results plant extracts were identified that were not mutagenic, not cytotoxic and that may be antimutagenic in the Ames test. For most plant extracts, at the highest concentration used (5 mg/ml), the level of antimutagenicity was below the recommended 45% to conclude whether plants have good antimutagenic activity. However, in most screening studies for antimutagenesis, a 20% decrease in the number of revertants must be obtained in order to score the extract as active. Psoralea pinnata L. had the highest percentage antimutagenicity recorded in this study (76.67 and 99.83% in S. typhimurium TA98 and TA100 respectively) at assayed concentration of 5 mg/ml. The results indicate that investigating antioxidant activity and the number of antioxidant compounds in plant extracts could be a viable option in searching for antimutagenic compounds in plants.

The anti-arthritic, anti-inflammatory, antioxidant activity and relationships with total phenolics and total flavonoids of nine South African plants used traditionally to treat arthritis.

BACKGROUND: Oxidative stress predisposes the human and animal body to diseases like cancer, diabetes, arthritis, rheumatoid arthritis, atherosclerosis and chronic inflammatory disorders. Hence, this study seeks to determine the antioxidant, anti-inflammatory and anti-arthritic activities of acetone leaf extracts of nine South African medicinal plants that have been used traditionally to treat arthritis and inflammation. METHODS: The anti-inflammatory activity of the extracts was determined by investigating inhibition of nitric oxide production in lipopolysaccharide activated RAW 264.7 macrophages as well as 15-lipoxygenase enzyme inhibition. An anti-protein denaturation assay was used to determine the anti-arthritic properties of the extracts. The antioxidant activity was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethyl-benzthiazoline-6-sulfonic acid) (ABTS) radical scavenging assays and ferric reducing antioxidant power (FRAP). The total phenolic and total flavonoid concentration of extracts were determined by using standard methods. RESULTS: All extracts inhibited nitric oxide production in a dose-dependent manner in the LPS-stimulated RAW 264.7 macrophages. Extracts of Maesa lanceolata and Heteromorpha arborescens inhibited NO production by 99.16 % and 89.48 % at a concentration of 30 µg/ml respectively. Elaeodendron croceum and Calpurnia aurea extracts had strong activity against 15-lipoxygenase activity with IC50 values of 26.23 and 34.70 µg/ml respectively. Morus mesozygia and Heteromorpha arborescens extracts had good in vitro anti-arthritic activity with IC50 values of 11.89 and 53.78 µg/ml, the positive control diclofenac sodium had IC50 value of 32.37 µg/ml. The free radical scavenging activity of the extracts in DPPH assays ranged between 7.72 and 154.77 µg/ml. Trolox equivalent antioxidant capacity (TEAC) and FRAP values ranged from 0.06 to 1.32 and 0.06 to 0.99 respectively. CONCLUSIONS: Results from this study support the traditional use of the selected medicinal plants in the management of arthritis and other inflammatory conditions. The free radical scavenging capacity of the extracts may be related to an immune boosting potential.

Antimicrobial activity and cytotoxicity of triterpenes isolated from leaves of Maytenus undata (Celastraceae).

BACKGROUND: Plants of the genus Maytenus belong to the family Celastraceae and are widely used in folk medicine as anti-tumour, anti-asthmatic, analgesic, anti-inflammatory, antimicrobial and anti-ulcer agents, and as a treatment for stomach problems. The aim of this study was to isolate and identify active compounds with antifungal activity from Maytenus undata after a preliminary study highlighted promising activity in crude extracts. METHODS: Sequential extracts of M. undata leaves prepared using hexane, dichloromethane (DCM), acetone and methanol (MeOH) were tested for activity against Cryptococcus neoformans, a fungal organism implicated in opportunistic infections. Bioassay-guided fractionation of the hexane extract using C. neoformans as test organism was carried out to isolate antifungal compounds. The cytotoxicity of compounds isolated in sufficient quantities was evaluated using a tetrazolium-based colorimetric cellular assay (MTT) and a haemagglutination assay (HA). RESULTS: The hexane extract was most active with an MIC of 20 µg/ml against C. neoformans. The triterpene compounds friedelin (1), epifriedelanol (2), taraxerol (3), 3-oxo-11α-methoxyolean-12-ene-30-oic acid (4), 3-oxo-11α-hydroxyolean-12-ene-30-oic acid (5) and 3,11-dihydroxyolean-12-ene-30-oic acid (6) were isolated. Compound 6 was isolated for the first time from a plant species. The antimicrobial activity of compounds 1, 3, 5 and 6 was determined against a range of bacteria and fungi implicated in opportunistic and nosocomial infections. Compounds 5 and 6 were the most active against all the tested microorganisms with MIC values ranging between 24 and 63 µg/ml, except against Staphylococcus aureus which was relatively resistant. Compounds 1 and 3 had a low toxicity with an LC50 > 200 µg/ml towards Vero cells in the MTT assay. Compounds 5 and 6 were toxic with LC50 values of 6.03±0.02 and 2.98±0.01 µg/ml, respectively. Compounds 1 and 3 similarly were not toxic to the red blood cells (RBCs) but compounds 5 and 6 were toxic, showing HA titer values of 1.33 and 0.67 respectively. CONCLUSIONS: Compounds 5 and 6 were the most active but were also relatively cytotoxic to monkey kidney cells and red blood cells, while the other isolated compounds were less active and less cytotoxic.