Department of Chemistry; Addis Ababa University; P.O.Box 30270, Addis Ababa, Ethiopia.

Keywords: Medicinal plants, Ethiopia

Many African countries offer a largely untapped source of potentially useful natural products with numerous species waiting to be documented and investigated. Contributions from our laboratory to the phytochemical study of medicinal and other plants of Ethiopia is presented here briefly.

Institut de Chimie des Substances Naturelles, CNRS, 91198 Gif-sur-Yvette, France.

Keywords: Antimitotic properties, Tubulin, Kopsia singapurensis, rhazinilam, Garcinia species, xanthones

ABSTRACT:

Starting from the discoveries of navelbine and taxotere, two potent analogs of natural antitumour compounds, the search of new antitumour drugs has continued at Gif-sur-Yvette, by associating classical cytotoxicity assays with other mechanism involved in the cell replication pathway. The tubulin-microtubules system, an easy and efficient method, is one of the targets used in finding new antimitotic drugs. Through various research programmes in tropical countries and in the framework of the long-term cooperation between the University of Malaya and CNRS, a number of molecules have been shown to possess activity on tubulin. Among them, rhazinilam, isolated from a Malaysian Kopsia, K. singapurensis Ridley, Apocynaceae. It has specific activity on microtubules. Studies of structure-activity relationships guided by the tubulin-test have led to a better knowledge of the properties of rhazinlam and to the design of analogs. Cytotoxic prenylxanthones have also been isolated from Vietnaamese Garcinia, G. nigrolineata (Clausiaceae). Nigrolineatin and its analogues possess anti-oncogene activity on FPTase. Other xanthone derivatives like xanthochymol were isolated from a Malaysian Garcinia, G. pyrifera and were found to possess activity on tubulin. Structure-activity relationships studies on these series have been done.

Natural Products Research Group, Department of Chemistry, University of Natal, Durban, 4041, South Arica and ¹Laboratory of Pharmacology, EES Sciences, University of Antananarivo, BP906, Antananarivo, Madagascar.

Keywords: Ptaeroxylaceae, Ptaeroxylon obliquun, Cedrelopsis grevei, Cneoraceae, Neochamaelea pulverulrenta (syn Cneorum pulverulentum), coumarins, chromones, diterpenoid, limonoid, derivative, cedmiline, cedmilinol, cneorun X.

Compounds isolated from the Ptaeroxylaceae family are discussed. The similarity of compounds isolated from Ptaeroxylon obliquum and Cedrelopsis grevei of the Ptaeroxylaceae family and from Cneorum tricoccon and Neochamaelea pulverulenta of the Cneoraceae family suggests a very close relationship between these families.

Department of Chemistry, University of Botswana, Private Bag 0022, Gaborone, Botswana and Department of Organic Chemistry, University of Yaounde, B.P. 812, Yaounde, Cameroon.

Keywords: Marketed plants, Hagenia abyssinica, Rosaceae, Dorstenia species, Moraceae, chemical constituents.

Different strategies have been developed by various research groups to determine a sound and practical basis for the selection of plants for scientific examination. Groups involved in drug discovery programs often use bioassay-guided fractionation to track, isolate and identify substances that have positive activity. Others employ ethnomedical information as leads. More recently combinatorial chemistry and high throughout robotic screening techniques have been employed mostly by the big multinational pharmaceutical companies. Each one of these approaches has it benefits and disadvantages and the selection depends upon the goals of the project and the resources available to the researchers. The selection of plant material for investigation by our research group has been guided the belief that plants that have acquired the status of marketed commodities have already been screened by traditional methods. This approach has led us to examine a number of plants and the results obtained in the course of training students has been stimulating and exciting. This paper will deal with examples of marketed plants from a number of countries in eastern, central and southern Africa. It will be selective rather than comprehensive. Reference will be made to the historically important Ethiopian anti-parasitic plant Hagenia abyssinica, and other marketed plants of current interest like Aloes, the devil’s claw (Harpagophytum procumbens), Hypoxis spp. In addition results from our own laboratories will be presented Scilla nervosa (Burch) Jesssop sub-species rigidifiolia (Hyacinthaceae) is used in Zulu medicine to treat rheumatic fever and as purges for children. In Botswana the plant is alleged to enhance female fertility and to treat infections. The tubers yielded thirteen homoisoflavoniod (nine of which are new) and three-stilbene derivatives. Bulbine capitata V poellen (syn. B. Stenophylla Verdooorn) is used in Botswana as antibiotic. This plant us a rich source of furanonaphthoquinones, anthraquinones including knipholone type compounds which show interesting biological properties. We have investigated several species of Dorstenia (Moraceae): D. mannji, D. kameruniana, D. psiliris and D. poinsettifolia. They are rich sources of prenylated flavonoids, which undergo various cyclizations to yield furano-, pydrano-, and dihydropyrano derivatives. Rhamus prinoides L’Herit occurs widely in Africa and is commonly known as Gesho in Ethiopia and dogwood in southern Africa. We have reported several quinines, flavonoids and naphthalenic compounds from various parts of this plant and have established that geshoidine may be the flavoring principle of the plant responsible for the characteristic bitter tastes of the domestic beverages Tella and Tej. Further examinations of the more polar fractions of (Rhamnaceae) have yielded acylated glycosides of emodin and emodin anthrone. Rhus pyroides (Anacadiaceae) is a plant whose leaves are carefully avoided by the corn cricket. Examination of this plant has yielded novel bichalcones, which may have potential insecticidal properties. Marketed plants that are collected from the wild run a great risk of extinction. This lecture will urge the need to developed substainable use of these important plants.

Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Obafemi Awolowo University, Ile—Ife, Nigeria

Email: [email protected]

Keywords: Piliostigma thonningii, Piliostigma reticulatum, Mitracarpus scaber, Staphylococcus aureus, Candida pseudotropicalis, Antibacterial and anti-inflammatory activities.

Amongst Nigerian plants with bioactivity are Piliostigma and Mitracarpus species. Ethyl acetate fraction of Piliostigma thonnigii contains C-methylflavonols as compounds responsible for both the antibacterial and anti-inflammatory activities of the leaves. Mitracarpus scaber has naphthoquinones known to possess a wide range of biological actions including antibacterial and antifungal activities.

Department of Chemistry, University of Venda, Private Bag X5050, Thohoyandou, 0950, South Africa; Department of Chemistry, University of Natal, Scottville, South Africa.

Keywords — Warburgia salutaris; Canellaceae; salutarisolide; warburganal; muzigadial; polygodial; isopolygodial; NMR; INAPT; NOE; COSY.

The stem bark of Warburgia salutyaris (Bertol. F. Chiov.) collected in Zoutpansberg mountains, South Africa, yielded a new drimane sessquiterpenoidd lactone, salutarisolide, along with four known drimane sesquiterpenoids warburganal, mukaadial, polygodial and isopolygodial. The structure of salutarisolide was fully characterized from its spectral data. The lactone is structurally related to muzigadial.

Department of Pharmacognosy and Drug Development and ¹Department of Biological Sciences, Ahmadu Bello University, Zaria, Nigeria.

Keywords: Carissa edulis, Pharmacognostic characters, Apocynaceae

C. edulis is used in traditional medicine in the treatment of toothache, chest complaints cough, stomach ulcer, lumbago, inflamed glands worms and as aphrodisiac. Macroscopical, microsopical and chemo-microscopical examinations have been carried out on the stem (powdered bark and anatomical sections). Also evaluative parameters, ash value, acid insoluble ash, moisture content and extractive values were determined. This could serve in the identification and preparation of a monograph on the plant.

Department of Pharmacognosy and ¹ Department of Pharmacology, Faculty of Pharmaceutical Sciences, University of Jos, Jos, Plateau State, Nigeria.

Keywords: Daniellia oliveri, rats, guinea pigs, stem bark, anti-ulcer, anti-cholinergic

The MeOH extract of Daniellia oliveri showed a dose related activity on the induced ulcers. The 500mg/kg extract had an activity (P<0.05) compared with vehicle. The reference drug, cimedtidine, used in the test at 100mg/kg did not show any activity in the ASA-induced ulcers. The effect of the extract on acetylcholine (Ach) induced contraction on rat duodenum was also assessed. Like the reference antagonist, atropine, used in the test, the extract showed a non-competitive antagonism on the induced contraction. This anti-spasmodic effect of the extract could partly explain the anti-ulcer effect. This is the first report on the anti-ulcer activities of the methanolic extract of D. oliveri stem bark.

Department of Pharmacology & Clinical Pharmacy

Faculty of Pharmaceutical Sciences, Ahmadu Bello University, Zaria, Nigeria

*Present address: Department of Pharmacology, Obafemi Awolowo University, Ile-Ife, Nigeria

Keyword: Azadirachta indica, Meliaceae, malaria, antipyretic, analgesic, anti-inflammatory, aggregatory activities.

Three crude extracts from Azadirachta indica leaves were assessed on various signs and symptoms of infection in vivo and in vitro. The methanolic and diethylether extracts have significant antipyretic, analgesic, anti-inflammatory and anti-aggregatory activities, while the chloroform extract did not show appreciable effect. The crude extracts compared favourably with chloroquine in pyrexia, indomethacin in platelet aggregation and acetylsalicylic acid (ASA) in analgesia and inflammatory experimental models. The pharmacological effects of these extracts might explain the effectiveness of A. indica leaf in malaria therapy traditionally.

Department of Phartmacognosy, Faculty of Pharmacy, College of Medicine, University of Ibadan, Nigeria. ¹Department of Pharmacognosy, Faculty of Pharmacy, Obafemi Awolowo College of health Sciences, Ogun State University, Sagamu, Nigeria.

Keywords: Cassia species, Leguminosae-Caesalpinoideae, Anthraquinone content, Laxative activity, Antimicrobial activity.

Colorimetric estimation of anthraquinone content, antimicrobial and laxative effects of leaves and pods of Cassia fistula Linn., C. specatabilis DC and C podocarpa Guill. and Perr. are described because of the popular uses of these species by herbalists in Ibadan. The pods of the Cassia species exhibited potent antifungal activity than the leaf samples. Pods of C. fistula showed significant antibacterial activity when compared to that of ampicillin. This study justifies the use of the Cassia species in traditional medicine.

Department of Pharmacognosy, Faculty of Pharmacy, University of Benin, Benin-City, Nigeria.