Background: The aim of this study was to evaluate the antimicrobial activity and the cytotoxicity of the ethanol crude extract, fractions and isolated compounds from the twigs ofEriosema robustum, a plant used for the treatment of coughs and skin diseases.Methods: Column chromatographic and spectroscopic techniques were used to isolate and identify eight compounds, robusflavones A (1) and B (2), orostachyscerebroside A (3), stigmasterol (4), 1-O-heptatriacontanoyl glycerol (5), eicosanoic acid (6), 3-O-β-D-glucopyranoside of sitosterol (7) and 6-prenylpinocembrin (8), fromE. robustum. A two-fold serial microdilution method was used to determine the minimum inhibitory concentration (MIC) against fungi and bacteria, and the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide reduction assay was used to evaluate the cytotoxicity.Results: Fraction B had significant antimicrobial activity againstAspergillus fumigatusandCryptoccocus neoformans(MIC 0.08 mg/ml), whilst the crude extract and fraction A had moderate activity againstA. fumigatusandCandida albicans(MIC 0.16 mg/ml). Fraction A however had excellent activity againstStaphylococcus aureus(MIC 0.02 mg/ml),Enterococcus faecalisandEscherichia coli(MIC 0.04 mg/ml). The crude extract had significant activity againstS. aureus,E. faecalisandE. coli. Fraction B had good activity againstE. faecalisandE. coli(MIC 0.08 mg/ml). All the isolated compounds had a relatively weak antimicrobial activity. An MIC of 65 μg/ml was obtained with robusflavones A (1) and B (2) againstC. albicansandA. fumigatus, orostachyscerebroside A (3) againstA. fumigatus, and robusflavone B (2) againstC. neoformans. Compound8had the best activity against bacteria (average MIC 55 μg/ml). The 3 fractions and isolated compounds had LC₅₀values between 13.20 to > 100 μg/ml against Vero cells yielding selectivity indices between 0.01 and 1.58.Conclusion: The isolated compounds generally had a much lower activity than expected based on the activity of the fractions from which they were isolated. This may be the result of synergism between different compounds in the complex extracts or fractions. The results support the traditional use ofE. robustumto treat infections. The crude extract had a good activity and low preparation cost, and may be useful in topical applications to combat microbial infections.

Antimicrobial resistance is a serious threat against humankind and the search for new therapeutics is needed. This study aims to investigate the antimicrobial and antioxidant activities of ethanol extracts and compounds isolated from Dissotis senegambiensis and Amphiblemma monticola, two Cameroonian Melastomataceae species traditionally used for the treatment of fever, malaria and infectious diseases. The plant extracts were prepared by maceration in ethanol. Standard chromatographic and spectroscopic methods were used to isolate and identify fourteen compounds from the two plant species [1–6 (from D. senegambiensis), 3, 4 and 7–14 (from A. monticola)]. A two-fold serial micro-dilution method was used to determine the minimum inhibitory concentration (MIC) against four bacterial strains including two resistant bacterial strains, methicillin resistant S. aureus (MRSA3) and methicillin resistant S. aureus (MRSA4) and three yeast strains. The fractionation of EtOH extracts afforded fourteen compounds belonging to triterpenoid and phenolic derivatives. The ethanol extracts, compounds 3, 5–8, 10 and the mixture of 10 + 12 were active against all the tested bacterial and fungal species. Compound 7 (MIC = 16–32 μg/mL) and 10 (MIC = 8–16 μg/mL) displayed the largest antibacterial and antifungal activities, respectively. Compounds 7, 10 and the mixture of 10 + 12 showed prominent antibacterial activity against methicillin- resistant S. aureus (MRSA) which is in some cases equal to that of ciprofloxacin used as reference antibacterial drug. Compound 8 also showed high radical-scavenging activities and ferric reducing power when compared with vitamin C and butylated hydroxytoluene used as reference antioxidants. The tested samples were non-toxic to normal cells highlighting their good selectivity. The result of this investigation reveals the potential of D. senegambiensis and A. monticola as well as the most active compounds in the search for new antimicrobial and antioxidant agents. So, further investigations are needed.

Natural products, including those derived from higher plants have, over the years, contributed greatly to the development of modern therapeutic drugs. Due to the medicinal importance in traditional practice and the diversified biology and chemistry of the constituents from Artemisia spp., the genus has been receiving growing attention. The aim of this study was to investigate the ability of the ethanol extract, four fractions (F1–F4) and five compounds namely artemisinin (1), scopoletin (2), chrysosplenetin (3), eupatin (4) and 3-O-β-d-glucopyranoside of sitosterol (5) isolated from A. annua to modulate the activity of anticholinesterase (AchE) and the production of nitric oxide (NO) in LPS-activated RAW 264.7 macrophages. At the lowest concentration tested (6.25 µg/mL), the crude extract and fraction F2 had the highest NO inhibitory activity (72.39 and 71.00 % inhibition respectively) without significant toxicity on the viability of macrophage cells (93.86 and 79.87 % of cell viability respectively). The crude extract inhibited AchE activity by 71.83 % (at 1 mg/mL) with an IC50 value of 87.43 µg/mL while F2 and F4 were the most active fractions (IC50 values of 36.75 and 28.82 µg/mL). Artemisinin (1) and chrysosplenetin (3) had the highest AChE activity with 71.67 and 80.00 % inhibition (at 0.1 mg/mL) and IC50 values of 29.34 and 27.14 µg/mL, respectively. Our results validate the traditional use of A. annua and could help to support the usefulness of this plant in the treatment of inflammatory and neurological disorders especially where nitric oxide and a cholinesterase are involved.

BackgroundWe decided to investigate the antimicrobial and the antioxidant activities of extracts and compounds isolated from Dissotis perkinsiae, Adenocarpus mannii and Barteria fistulosa, three Cameroonian medicinal plants used for the treatment of skin diseases, wounds, fever, rheumatism, malaria and/or infectious diseases.MethodsStandard chromatographic and spectroscopic methods were used to isolate and identify ten compounds from the three plant species [1–5 (from D. perkinsiae), 2, 6–8 (from A. mannii) and 2, 4, 9, and 10 (from B. fistulosa)]. A two-fold serial microdilution method was used to determine the minimum inhibitory concentration (MIC) against a panel of fungal and bacterial species. The radical scavenging capacity using 2,2-diphenyl-1-picryhydrazyl (DPPH) was determined to evaluate the antioxidant activity of the samples.ResultsThe compounds isolated were: ursolic acid (1), oleanolic acid (2), quercetin 3-O-(6″-O-galloyl)-β-galactopyranoside (3), 3-O-β-d-glucopyranoside of sitosterol (4), ellagic acid (5), isoprunetin (6), chrysin 7-O-β-d-glucopyranoside (7), isovitexin (8), hederagenin (9) and shanzhiside methyl ester (10). The ethanol extract of D. perkinsiae had good antibacterial activity against Enterococcus faecalis (MICs 0.04 and 0.08mg/ml), Escherichia coli (MIC 0.08mg/ml) and Staphylococcus aureus (MIC 0.08mg/ml). The extract of B. fistulosa had significant antifungal activity against Cryptococcus neoformans with an MIC of 0.08mg/ml. Other extracts had moderate to poor antimicrobial activities with the MIC ranging from 0.16 to 2.50mg/ml. The isolated compounds were generally more active against bacteria (MIC ranging from 16 to 250μg/ml) than fungi (MIC between 31 and 250μg/ml). Moderate antibacterial activity was obtained with compound 3 against E. faecalis and E. coli (MIC of 16μg/ml in both cases), compounds 6 and 10 against E. faecalis (MIC of 16μg/ml), and compound 9 against E. faecalis (MIC 31μg/ml) and S. aureus (MIC 31μg/ml). The B. fistulosa extract had the greatest radical scavenging activity (IC50 100.16μg/ml) followed by extracts of D. perkinsiae (IC50 130.66μg/ml), and A. mannii (IC50 361.30μg/ml). Compounds 3 and 5 had significant antioxidant activities with the IC50 of 9.84 and 9.99μg/ml as compared to that of ascorbic acid (IC50 2.41μg/ml).ConclusionThe results obtained support the traditional use of the three plant species (D. perkinsiae, A. mannii and B. fistulosa) in traditional medicine for the treatment of infections. Some extracts and isolated compounds could be useful in development of antimicrobial agents. We are currently investigating the toxicity and other pharmacological activities with the potential use as topical antimicrobial agents