Abraham Yeboah Mensah

Chemical Diversity of Lippia multiflora Essential Oils from West Africa

Abstract The essential oil content, composition and the physicochemical properties of Lippia multiflora leaves from twelve different regions in Ghana were characterized in this study. The Ghanaian oils showed a significant variability in their chemical composition and five chemotypes were identified. The oil from Aframso Bridge was yellow with a refractive index (RI) of 1.4853, density (DE) of 0.894 and was dominated by linalool (29%) and germacrene D (28%) with fresh, and slightly medicinal and spicy aroma. Ghanaian samples from Seikwa, Buem Nsuta and Golokwati were characterized by high levels of sesquiterpenes (45–70%). The aroma was medicinal/herbaceous and the color was typically yellow, except the oil from Seikwa which was dark orange-yellow, RI ranging from 1.4920 to 1.5043 and DE 0.893 to 0.93 D. The oils from Nyankpala, Sari, Amantin, Atebubu and Kobre contained high levels of aromatic monoterpenes (p-cymene 14–19%, thymol 30–40%, and thymyl acetate 14–17%). The oils were characterized as spicy and the color ranged from dark yellow (Nyankpala, Sari and Kobre) to yellow (Atebubu and Amantin) (RI 1.4969 to 1.5020, DE 0.9207 to 0.9344). The oil from Ho showed lower levels of aromatic monoterpenes and higher levels of farnesol, the oil was yellow and aroma woody/camphoraceous (1.492 RI, 0.893 D). In contrast, oils from Nsawkaw and Kofiase-Kubesiase were composed of high amounts of 1,8-cineole (43–47%), sabinene (12–15%, respectively), and were light yellow (RI 1.4695 to 1.4712, DE 0.8995 to 0.9002). A cluster analysis was performed for comparison and characterization of L. multiflora oils from Ghana other 33 oils from 10 African countries. The oils from Ghana with these five chemotypes appeared to be the most diverse oils in Sub-Saharan Africa.

Erythroivorensin: A novel anti-inflammatory diterpene from the root-bark of Erythrophleum ivorense (A Chev.)

The stem- and root-bark of Erythrophleum ivorense (A Chev., family, Fabaceae) are routinely employed in the West African traditional medicine to treat inflammation and a variety of other disease conditions. Although the chemistry and pharmacology of cassaine-type diterpene alkaloids isolated from the stem-bark of the plant are fairly established, the root-bark has not yet been investigated. In the present study, the crude aqueous-alcohol extract of the root-bark was demonstrated to display a time- and dose (30-300 mg/kg p.o.)-dependent anti-inflammatory effect in chicks. Comprehensive chromatographic analysis coupled with spectroscopic and X-ray study further allowed the assignment of one of the major anti-inflammatory constituents as a novel cassaine-type diterpene, erythroivorensin. The other major constituents were known anti-inflammatory compounds: a triterpene, betulinic acid and a flavonoid, eriodictyol. The dose (10-100mg/kg p.o.)-dependent anti-inflammatory effects of the three compounds were either comparable or more significant than the positive control, diclofenac.

Antiinflammatory properties of the stem-bark of Anopyxis klaineana and its major constituent, methyl angolensate.

Anopyxis klaineana (Pierre) Engl. (Rhizophoraceae) is one of the reputed West African folkloric medicines that has never been investigated for its pharmacological effects or phytochemical constituents. In the present study, the antiinflammatory properties of the stem‐bark extracts were evaluated using the carrageenan‐induced paw oedema model in chicks. The petroleum ether, ethyl acetate and methanol extracts all showed a time and dose‐dependent antiinflammatory effect over the 5‐h observation period. Phytochemical analysis of the most active extract (methanol extract) yielded the principal constituent that was identified as methyl angolensate through extensive spectroscopic and X‐ray analysis studies. Although slightly less potent (ED50, 4.05 ± 0.0034 mg/kg, orally) than the positive control, diclofenac (ED50, 2.49 ± 0.023, intraperitoneally n = 5), this first ever compound isolated from A. klaineana showed promising antiinflammatory activity that may account to some of the reported medicinal uses of the plant. Copyright

Antibacterial, Antioxidant and Anti-inflammatory Properties of Margaritaria discoidea, a Wound Healing Remedy from Ghana

a B S t r a c t Margaritaria discoidea (Baill.) Mull arg. (euphorbiaceae), has folkloric use in the treatment of wounds and skin infections. We report on the antibacterial, antioxidant and anti-inflammatory effects of the leaves and stem bark of Margaritaria discoidea. A 70% ethanolic extract of the various plant parts were tested for antibacterial activity using the agar well diffusion and micro dilution assays. Free radical scavenging, total antioxidant and phenol content were estimated. Using the carrageenan-induced foot pad oedema in chicks, the anti-inflammatory activity of the extract was assessed. The bark extract gave the higher activity with a zone of inhibition of 16.33 ± 0.88 mm against Bacillus subtilis. the Mic’s for the bark extracts ranged from 500 µg/mL to over 1000 µg/mL against the test organisms. However, the leaf extract had no activity against all organisms tested. The leaf and bark extracts demonstrated free radical scavenging activity yielding ic 50 values of 0.0185 and 0.0181 mg/mL respectively. In the total antioxidant assay, ascorbic acid equivalents ranged from 0.49 mg/g in the bark to 0.56 mg/g in the leaf. Both extracts had high phenolic content correlating with their antioxidant activity. The extracts showed significant anti-inflammatory activity. The ED 50 s of the leaf and bark extracts were 12.20 and 8.27 mg/kg body weight respectively. The results were comparable to those of diclofenac and dexamethasone, the reference drugs used in this study. on the basis of the antimicrobial, antioxidant and antiinflammatory activities observed for both extracts, the ethnomedicinal use of the plant in the mamagement of wounds and skin infections is supported.

Anti-inflammatory tirucallane triterpenoids from Anopyxis klaineana Pierre (Engl.), (Rhizophoraceae).

Phytochemical investigation of the stem bark extract of Anopyxis klaineana was carried out by various chromatographic techniques resulting in the isolation and characterization of three new tirucallane triterpenoids, namely 3,23-dioxotirucalla-7,24-dien-21-oic acid (1), 3,4-secotirucalla-23-oxo-4(28)7,24-trien-3,21-dioic acid (2) and 3,4-secotirucalla-4-hydroxy-23-oxo-7,24-diene-3,21-dioic acid-21-methyl ester (3), along with nine known compounds (4-12). The structural elucidation of the compounds was performed by means of high-resolution mass spectrometry (HRMS(n)), nuclear magnetic resonance (NMR), and by comparison to literature data. Although none of the isolated compounds showed antibacterial efficacy against selected environmental and clinically important pathogenic Gram-positive and -negative bacteria, they demonstrated moderate DPPH free radical scavenging properties. Furthermore, compounds 1 and 7 exhibited remarkable anti-inflammatory potential in a prostaglandin E2 (PGE2) competitive enzyme immunoassay with IC50 values of 3.63 μM and 10.23 μM, respectively.

Pharmacognostic standardisation of Hilleria latifolia (Lam.) H. Walt. (Phytolaccaceae)

ABSTRACT Objective To establish the pharmacognostic characters for the correct identification and quality control of Hilleria latifolia (H. latifolia), an important herb in Ghanaian folklore medicine, for the treatment of infections, pain and inflammation. Methods The macro-morphological, qualitative and quantitative microscopic features, physicochemical and phytochemical features of the medicinally used parts of H. latifolia were evaluated using standard methods. Results The plant has simple, alternate leaves with entire margin. The lamina is ovate to broadly lanceolate with an acuminate apex. It is hypostomatic with anomocytic stomata. The plant contains abundant prismatic crystals in all parts. Starch grains abound in the roots. The quantitative indices of the leaf and physicochemical parameters have also been established. Conclusions The pharmacognostic features established in this study may be used as part of the pharmacopoeial standard for the correct identification and quality control of H. latifolia.

Antimicrobial pentacyclic triterpenes and glycosides from the stem bark of Cussonia bancoensis

Abstract The stem bark of Cussonia bancoensis is used traditionally for the treatment of different types of infection and pain. A bioassay guided fractionation of the methanol stem bark extract led to the isolation of five pentacyclic triterpenes and glycosides identified based on spectroscopic data as 23-hydroxyursolic acid (CB1), hederagenin (CB2), 3-O-α-L-arabinopyranosyl-echinocystic acid (CB3), 3-O-α-L-arabinopyranosyl- oleanolic acid (CB4) and 3-O-α-L-arabinopyranosyl-ursolic acid (CB5). CB2 - CB5 are being reported for the first time from this species. The compounds were evaluated for antimicrobial activity against ten microorganisms using the HT-SPOTi method. CB3 demonstrated remarkable antimicrobial activity against S. aureus, S. pyogens, E. faecalis, S. typhi and C. albicans at MICs between 3.12 and 12.5 µg/mL. Among the studied compounds, it was observed that hydroxylation of position C-16 of the oleanane skeleton may enhance antimicrobial activity. This study gives insight into the anti-infective constituents of the stem bark of C. bancoensis and justifies its use in ethnomedicine.

Leishmanicidal activity of the root bark of Erythrophleum Ivorense (Fabaceae) and identification of some of its compounds by ultra-performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-QTOF-MS/MS)

ETHNOPHARMACOLOGICAL RELEVANCE Leishmaniasis is one of the neglected tropical disease caused by a protozoan of the genus Leishmania transmitted by sandflies. High cost and lack of oral formulation of existing drugs, rapid developments of resistance by the parasite coupled with serious side effects require new treatments to augment or replace currently available therapies. The major merits of herbal medicine seem to demonstrate perceived efficacy, low incidence of serious adverse effects and low cost. Erythrophleum plants possess beneficial biological properties and, as such, characterization of the bioactive components of these plants is imperative. Previous work has shown an overwhelming presence of cassaine alkaloids in these plants. However, amongst these plants, the African based specie (Erythrophleum ivorense) is the least studied. OBJECTIVE In the current study, the in vitro anti-leishmanial activity of the crude extract, its fractions and isolated compounds were evaluated using direct counting assay of promastigotes of Leishmania donovani using amphotericin B as positive control. MATERIALS AND METHODS The anti-leishmanial activity of E. ivorense extract was evaluated in vitro against the promastigote forms of Leishmania Donovani using a direct counting assay based on growth inhibition. Different crude extracts from ethyl acetate, pet-ether, and methanol as well as pure isolated compounds of E. ivorense: Erythroivorensin, Eriodictyol and Betulinic acid were screened. To know the possible components of the active methanolic extract, attempt was made to elucidate the extract using ultra-performance liquid chromatography quadrupole time of flight mass spectrometry (UHPLC-QTOF-MS/MS). RESULTS This afforded a weak pet-ether fraction, a moderately active ethyl acetate fraction and a significantly active methanol fraction (IC50 = 2.97μg/mL) compared to Amphotericin B (IC50 = 2.40±0.67μg/mL). The novel diterpene erythroivorensin, betulinic acid and the flavanone Eriodictyol, from the ethyl acetate fraction, showed weak activity. UPLC-QTOF-MS/MS was used to identify the cassaine diterpenoids from the active methanol fraction. Here, 10 compounds of this type were putatively identified from the ethanol crude extract. CONCLUSION The fragmentation mechanism of these metabolites is also proposed and are expected to serve as reference template for identification of these and related compounds in future. The presence of these compounds is an indication that they are an inherited and evolutionary component of plants belonging to the Erythrophleum genus. Our results further present another dimension where these compounds and their relative abundances can be used as chemo-taxonomical bio-markers of the genus. The present study also successfully demonstrated/re-affirmed the use of UPLC-QTOF-MS/MS as a robust technique for the characterization of natural products.

Protection effect of the anthraquinones, cassiatorin and aurantio-obtusin from seeds of Senna tora against cowpea weevil attack

Objective: To explore the potential insecticidal, ovipositor deterrent and antifeedant effects of ethyl acetate extract of the seeds of Senna tora (Syn. Cassia tora) against cowpea weevil (Callosobruchus maculatus). Methods: The activities were evaluated using standard protocols. In these bioassays, the cowpea seeds were used directly as an insect feed. The activity of the extract and isolated compounds were tested at concentrations of 100, 200 and 300 μg/mL and compared to neem oil and cinnamaldehyde (as standard positive controls). Phytochemical analysis of the ethyl acetate extract was done through a number of chromatographic techniques and the structures of the isolated compounds were established through comprehensive spectroscopic analysis including 2D-NMR and ESI-MS studies. Results: Fractionation of the active ethyl acetate extract resulted in the isolation of one known anthraquinone, aurantio-obtusin (1) and a novel compound that was named as cassiatorin (2). Compounds 1 and 2 showed comparable insect antifeedant properties with the positive controls while their insecticidal and ovipositor deterrent effects were far superior to the standard controls. Conclusions: It is thus concluded that Senna tora extracts and the isolated compounds (1 and 2) may be employed in the postharvest management of stored cowpea seeds and as other crop protectants.