Morinda lucida extract induces endothelium-dependent and -independent relaxation of rat aorta

Morinda lucida Benth (Rubiaceae): A review of its ethnomedicine, phytochemistry and pharmacology

ETHNOMEDICINAL RELEVANCE

Natural products derived from plants have served the primary healthcare needs of millions of indigenous people for centuries, many of which have been documented and scientifically validated. Morinda lucida Benth (Rubiaceae), also referred to as brimstone tree, is an ethnomedicinal plant which has been widely used in traditional medicine for several decades, particularly in the African continent. Various parts of the plant, including stem bark, leaves and root, have been applied in traditional medicine for the management of various pathological conditions such as malaria, diabetes, hypertension, inflammation, typhoid fever, cancer, cognitive disorders, sickle cell disease, trypanosomiasis, onchocerciasis and various fevers. In this review, we critically evaluated the relationship between traditional uses, laboratory pharmacological activities and clinical studies on M. lucida so as to unveil opportunities for the development of relevant therapeutic agents against diseases that threaten mankind.

MATERIALS AND METHODS

A search for relevant data on M. lucida was done using scientific databases (Google Scholar, Mendeley, ScienceDirect, PubMed, Asian Science Citation Database, Chinese Biomedical Literature Database, Chinese National Knowledge Infrastructure, Chinese Scientific Journal Database, Chinese Science Citation Database, other web sources (such as The Plant List and PROTA), books and other literature sources.

RESULTS

A hundred compounds have been isolated from M. lucida. Many of the reported secondary metabolites include alkaloids, tannins, anthraquinones, sterols, saponins, polyphenols, terpenoids, phenols and cardiac glycosides. The in vitro and in vivo experimental studies on various extracts, fractions and isolated compounds of M. lucida support the acclaimed pharmacological activities of the plant, such as antimalarial, antidiabetic, hypotensive, anti-inflammatory, immunostimulatory, antioxidant, antimicrobial, antiproliferative, cognitive-enhancement, anti-sickling, anti-trypanosomal, anti-onchocercal, muscle relaxant, antifungal and anti-leishmanial activities. These evidence-based scientific reports lend credence to their traditional uses. However, the safety of extracts of M. lucida is a cause for concern following reported toxicities such as antispermatogenic effect, genotoxicity and in vitro inhibition of human cytochrome P450 3A subfamily.

CONCLUSION

Documented evidence suggests that M. lucida remains a rich source of extracts and chemical compounds with diverse bioactivities that are of therapeutic benefit to man and this justifies its traditional uses for the primary healthcare needs of indigenous populations across tropical Africa. Due to the fact that M. lucida extracts may not be safe at some reported doses, more in-depth studies on their toxicities are required to better understand safer approaches to their traditional uses. In addition, mechanistic studies on the isolated compounds with known pharmacological activities are quite limited, thus necessitating future research efforts to be focused on the mechanisms of action of these active principles in order to facilitate their potential enlistment for rational drug design.

Hepatotoxicity and nephrotoxicity evaluation in Wistar albino rats exposed to Morinda lucida leaf extract

Background:

Aqueous extract of Morinda lucida benth leaf is consumed in Southern Nigeria in the treatment of malaria without any regard for its safety.

Aim:

The aim of the study was to investigate the effects of ingestion of the ethanolic leaf extract of the plant on liver and kidney functions in Wistar albino rats.

Materials and Methods:

Acute oral toxicity test was performed to determine the LD₅₀; sub-chronic toxicity study was then carried out by oral administration of different doses of the extract on daily basis to different groups of rats for 42 days. The animals were subsequently sacrificed, and liver and kidney functions assessed biochemically using standard techniques.

Results:

The acute oral toxicity result, LD_50, revealed Morinda lucida leaf extract to be non-lethal at 6400mg/kg body weight. The results obtained for liver and kidney function parameters indicated that ingestion of Morinda lucida leaf extract has no toxic effect on liver and kidney functions.

Conclusion:

The results can form the basis for clinical trials in humans.

Composition and Antioxidant Activities of Leaf and Root Volatile Oils of Morinda lucida

Morinda lucida (L.) Benth. (Rubiacae) is used in traditional medicine in many West African countries for the treatment of various human diseases. The leaves and roots of this plant were subjected to hydrodistillation to obtain volatile oils which were analyzed by high resolution GC/MS. Fifty compounds were identified in the leaf volatile oil and the major compounds were α-terpinene (17.8%) and β–bisabolene (16.3%). In the root oil, 18 compounds were identified, the major constituents being 3-fluoro- p-anidine (51.8%) and hexadecanoic acid (12.0%). Antioxidant activities of the oils were examined using the DPPH, ABTS, reducing power and lipid peroxidation assays. All assays were concentration dependent with varying antioxidant potentials. The antioxidant activity of the root volatile oil of M. lucida was similar to that of the standard drugs used.

Cytotoxic and genotoxic effects of aqueous extracts of five medicinal plants on Allium cepa Linn

The cytotoxic and genotoxic effects of aqueous extracts of five medicinal plants: Azadirachta indica (A. Juss), Morinda lucida (Benth.), Cymbopogon citratus (DC Stapf.), Mangifera indica (Linn.) and Carica papaya (Linn.) was evaluated using the Allium cepa assay. The extracts were prepared with tap water as practised locally. Onion bulbs were exposed to 1, 5, 10, 25 and 50%; and 1, 2.5, 5, 10 and 20% concentrations (v/v) of each of the extracts for macroscopic and microscopic analyses, respectively. There was concentration-dependent and statistically significant (P<0.05) inhibition of root growth by the extracts when compared with the control. The EC(50) obtained for decoctions of Azadirachta indica. Cymbopogon citratus, Mangifera indica and Carica papaya were 0.6, 3.0, 1.4 and 0.8%, respectively. It was 2.6 and 0.8% for the squeezed extracts of Azadirachta indica and Morinda lucida, respectively. All the tested extracts were observed to have mitodepressive effects on cell division and induced mitotic spindle disturbance in Allium cepa. These results suggest an inhibitory, mitodepressive and turbagenic activities of the aqueous extracts on Allium cepa.

A systematic review of mechanisms by which natural products of plant origin evoke vasodilatation

This article reviews the body of work aimed at elucidating the mechanisms of action by which natural products of plant origin exert a vasodilatory effect at the level of the vasculature. The search was restricted to 4 mechanisms: the nitric oxide system and (or) reactive oxygen species, the eicosanoid system, potassium channel function, and calcium channel function. The National Library of Medicine database was searched using "PubMed" without restriction to language. The search generated 266 references on 15 November 2005. Most studies were in vitro in nature and of these, most involved studies in the rat aorta. Many of the natural products evoked vasodilatation through an endothelium-dependent mechanism. The vasodilatation was attenuated or abolished by a nitric oxide synthase inhibitor and, in some of these studies, by an inhibitor of guanylate cyclase. A few studies reported a cyclooxygenase component, but most found no effect of the cyclooxygenase inhibitor, indomethacin. The vasorelaxation evoked by several natural products was attenuated by various potassium channel blocking agents, suggesting that some natural products exerted their effect either directly or indirectly through activation of potassium channels. Finally, a significant number of natural products evoked vasodilatation either through blockade of calcium channels or by inhibiting the release of calcium from intracellular stores. Many natural products evoked vasodilatation through multiple mechanisms. The information in this review on mechanisms of action should facilitate good clinical practice by increasing the predictive capabilities of the practitioner, notably the ability to predict adverse effects and interactions among medications. The knowledge should also help to provide leads to the ultimate goal of developing new therapeutic medications.