Phytochemical and Pharmacological Studies of some Medicinal Plants from Tanzania

Joseph J. Magadula*, Ester Innocent, Zakaria H. Mbwambo and Modest C. Kapingu Institute of Traditional Medicine, Muhimbili University of Health and Allied Sciences, P. O. Box 65001, Dar es Salaam, Tanzania *Corresponding author International Journal of Current Research and Academic Review ISSN: 2347-3215 Volume 2 Number 10 (October-2014) pp. 99-111 www.ijcrar.com Int.J.Curr.Res.Aca.Rev.2014; 2(10):99-111 100 properties to fight disease causing pathogens. Microorganisms are frequently a cause of prevailing diseases, presenting a serious public health issue in a significant segment of the population as showed by both private and official health care systems in Tanzania and around the global. On the other hand, chronic diseases like HIV/AIDS and cancer have raised the world’s health crisis due to both their emergent and long‐term development. Cancer cases distribution shows no differences in its epidemiology in all regions of the world whereas, HIV/AIDS have affected the world excessively and the greatest burden being in sub-Saharan Africa (WHO, 2008). Currently, about 80% of the populations in developing countries use traditional medicine for their healthcare (Bannerman et al., 1983) with at least 25% of drugs been derived from plants. This necessitates the demand for the development of new drugs particularly of plant origin. Our efforts to investigate into the phytochemistry of the Tanzanian medicinal plants have led to the isolation of many secondary metabolites of intriguing chemical structures as well as noticeable biological activities. This paper reviews our investigations for natural products from some Tanzanian medicinal plant species during the past 7 years, some of the compounds having unusual chemical structures and important biological properties Plants Investigated Our focus was mainly to investigate plants that are not studied but have reported for use in traditional medicine as well as those which are endemic to Tanzania. Furthermore our choice was also guided by the ethnomedical information obtained from the plant locality as well as the chemotaxonomical and/or ethnobotanical information. Table 1 indicates the status of the investigated plants whereby seven (7) plants were indigenous, two (2) were exotic and seven (7) were endemic to Tanzania. Phytochemistry Different chromatographic techniques were employed during the phytochemical work of the plants under this study. These include column chromatography, preparative column chromatography, size exclusion technique and high performance liquid chromatography. Structure elucidation and identification of the isolated compounds were made possible by using spectroscopic facilities obtained from our collaborators in Germany and France. Our results revealed the presence of different classes of natural products that are classified in the following broad structural categories namely alkaloids, benzophenones, coumarins, flavonoids, limonoids, terpenoids, xanthones and other classes (Table 2). Alkaloids Alkaloid is a class of naturally occurring organic nitrogen-containing bases. They are known to have diverse and important physiological effects on humans and other animals. Although the chemical structures of alkaloids are extremely variable, they contain at least one nitrogen atom in an amine-type structure. The well-known alkaloids that have high application in modern medicine include vincristine, vinblastine, morphine, strychnine, quinine, ephedrine and nicotine (Wink, 1998). Our investigations on three Tanzanian medicinal plants (Annona senegalensis, Annona squamosa and Teclea amaniensis) resulted into isolation of nine (9) alkaloids. Int.J.Curr.Res.Aca.Rev.2014; 2(10):99-111 101 Table.1 List of Plants investigated under study S/N Plant* Family Place of collection/Region Part collected Voucher specimen 1 Annona senegalensis I Annonaceae Changanyikeni/DSM Leaves OT 00352 2 Annona squamosa X Annonaceae Bunju/DSM Leaves OT 00353 3 Baphia kirki E** Fabaceae Pugu/DSM Stem EBM601 4 Baphia puguensis E** Fabaceae Pugu/DSM Root EBM 560 5 Antidesma venosum I Euphorbiaceae Handeni/Tanga Root & Stem HOS 974 6 Croton jatrophoides I Euphorbiaceae Pande/DSM Root ZHM 12576 7 Dalbergia vacciniifolia I Fabaceae Changanyikeni/DSM Stem FM 1682 8 Allanblackia ulugurensis E Clusiaceae Morningsite/Moro Stem BM 6401 9 Garcinia edulis X Clusiaceae Amani/Tanga Root HOS 3426 10 Garcinia semseii E Clusiaceae Kihansi/Iringa Stem FM 1629 11 Garcinia volkensii I Clusiaceae Amani/Tanga Stem HOS 3409 12 Mammea usambarensis E Clusiaceae Shagayu/Tanga Stem & Fruits SM 732 13 Harrisonia abyssinica I Simaroubaceae Mza/DSM Root & Stem HSO 5627 14 Milletia puguensis E Leguminosae Pugu/DSM Root EBM 561 15 Teclea amanuensis E Rutaceae Amani/Tanga Stem FM1321 * E = Endemic, I = Indigenous, X = Exotic ** = threatened by habitat loss Int.J.Curr.Res.Aca.Rev.2014; 2(10):99-111 102 Table.2 List of compounds isolated Class Name Source Part Alkaloids (-)-Roemerine (1) Annona senegalensis Leaves Annonaine (2) A. squamosa Leaves Tecleamaniensine A (3) Teclea amaniensis Stem Tecleamaniensine B (4) T amaniensis Stem Amaniensine (5) T amaniensis Stem Dictamnine (6) T amaniensis Stem Kokusaginine (7) T amaniensis Stem Evoxanthine (8) T amaniensis Stem Benzophenone Semsinones A (9) Garcinia semseii Stem Semsinones B (10) G. semseii Stem Semsinones C (11) G. semseii Stem Guttiferone A (12) G. semseii Fruit hulls Guttiferone K (13) G. semseii Fruit hulls Guttiferone F (14) Allanblackia ulugurensis Root 30-epi-cambogin (15) A. ulugurensis Root Coumarins Mammea B/BB (16) Mammea usambarensis Stem Mammea B/BD (17) M. usambarensis Stem Mammea B/AB (18) M. usambarensis Fruit Mammea B/AB cyclo D (19) M. usambarensis Fruit Flavonoids Puguflavanone A (20) Baphia puguensis Root Puguflavanone B (21) B. puguensis Root Erythrisenegalone (22) B. puguensis Root 6,2'-dimethoxy-7,4'-dihydroxyisoflavone (23) Dalbergia vacciniifolia Stem 6,2',4'-trimethoxy-7-hydroxyisoflavone (24) D. vacciniifolia Stem 6,2',4',5'-tetramethoxy-7-O-[β−D-apiofuranosyl-(1→6)β−D-glucopyranoside] isoflavone (25) D. vacciniifolia Stem 6,2',4',5'-tetramethoxy-7-hydroxyisoflavone (26) D. vacciniifolia Stem Morelloflavone (27) Garcinia volkensis Stem Limonoids Harrisonin (28) Harrisonia abyssinica Root Pedonin (29) H. abyssinica Root Terpenoids Achilleol A (30) Garcinia semseii Stem Int.J.Curr.Res.Aca.Rev.2014; 2(10):99-111 103 Isoteucvin (31) Croton jatrophoides Root Jatrophoidin (32) C. jatrophoides Root Penduliflaworosin (33) C. jatrophoides Root Teucvin (34) C. jatrophoides Root Lupeol (35) Garcinia edulis Root Lupeol acetate (36) Garcinia edulis Root Betulinic acid (37) A. venosum Root Friedelin (38) Garcinia edulis Root Epifriedelanol (39) A. venosum Root Xanthones Baphikixanthones A (40) Baphia kirkii Stem Baphikixanthones B (41) B. kirkii Stem Baphikixanthones C (42) B. kirkii Stem Garceduxanthone (43) Garcinia edulis Root Forbexanthone (44) G. edulis Root Isorheediaxanthone B (45) Garcinia volkensis Stem 12-hydroxy-des-D-garcigerrin A (46) G. volkensis Stem Rheediaxanthone B (47) G. volkensis Stem Other compounds 3-hydroxy-5-methoxybiphenyl (48) Allanblackia ulugurensis Stem 3-Methoxy-8,9-methylenedioxypterocarpene (49 Baphia puguensis Root 4-hydroxy-3-methoxycinnamate (50) B. puguensis Root Baphikinone (51) Baphia kirkii Stem (3R,4R,5S)-4-hydroxy-5-methyl-3-tetradecanyl γlactone (52) A. venosum Stem Int.J.Curr.Res.Aca.Rev.2014; 2(10):99-111 104 From the ethyl acetate of the leaves of A. senegalensis and A. squamosa we isolated (-)-roemerine (1) (You et al., 1995) and annonaine (2) (Miski et al., 1995) respectively, while from the stem bark of an East African medicinal plant, Teclea amaniensis we isolated two novel furanoquinoline alkaloids named tecleamaniensine A (3) and tecleamaniensine B (4) as well as an acridone alkaloid, amaniensine (5), in addition to dictamnine (6), kokusaginine (7) and evoxanthine (8). Compounds 6, 7 and 8 were previously reported from Teclea natalensis (Tarus et al., 2005), Comptonella sessifoliola (Pusset et al., 1991) and Vepris sclerophylla (Rasoanaivo et al., 1999) respectively. The chemical structures of compounds 1-8 are presented in Fig. 1. Benzophenones Our phytochemical investigation on some Tanzanian Garcinia species revealed the presence of benzophenones. This class gives a series of oxidized and isoprenylated compounds that are believed to originate from the mixed shikimate and acetate biosynthetic pathways (Beerhues and Liu, 2009). Many benzophenone compounds from the genus Garcinia contains the cyclohexatrione moiety, which is generated by incorporation of several isoprenyl groups into C-2 and C-4 of a 1,3,5-trihydroxybenzophenone to form a bicyclo[3.3.1]nonane (Oliveira et al., 1999). This type of bridged polycyclic skeletons is widely distributed in the genus Garcinia and they are associated with a wide range of biological and pharmacological activities (Wu et al., 2008). This type of compounds has been isolated from Tanzanian plant species of the family Clusiaceae. Investigation from the ethanol extract of the stem bark of Garcinia semseii gave four isoprenylated benzophenones, named semsinones A-C (9-11), while study on the fruit hulls of G. semseii yielded guttiferones A (12) and K (13). We also investigated the stem bark of Allanblackia ulugurensis that afforded guttiferone F (14) and 30-epi-cambogin (15). Their structures were established using spectral data and by comparison with the closely related compounds reported in the literature (Fig. 2).