Antioxidant and Vascular Relaxation Activities of Tropical Plant Extracts

In this study, the methanolic extracts of twelve plants which are the leaves of noni (Morinda citrifolia L.), maman (Gynandropsis gynandra L.), cashew (Anacardium occidentale L.), sweet potato (Ipomoea batatas L.), papaya (Carica papaya L.), mint (Mentha arvensis L.), semambu (Azadirachta indica), betel (Piper betle L.); lemongrass stalk (Cymbopogon citrates Stapf.), bird chili fruit (Capsicum frutescens L.), roselle calyx (Hibiscus sabdariffa), and oil palm frond (Elaeis guineensis Jacq.) were analyzed for in vitro antioxidant and vascular activities. Their total phenolic content was also estimated. Plant extract showing high antioxidant and vascular relaxing activities were further tested for their in vivo antioxidant and cholesterol lowering effects in hypercholesterolemic New Zealand White rabbits.In vivo antioxidant test (ferric reducing/antioxidant potential [FRAP] assay) showed the highest activity in cashew leaf extract (4.3 mmol FRAP/g d.w.) and the lowest in lemongrass extract (0.2 mmol FRAP/g d.w). The antioxidant activity of the cashew leaf extract was equivalent to those of green tea extract while lemongrass extract's antioxidant activity was equivalent to those of purified apigenin. The total phenols ranged from 55-256 mg gallic acid equivalent / g dry weight (d.w.) extracted samples with the highest concentration in oil palm frond extract. In this study, the antioxidant activity of the extracts did not correlate with the total phenolic contents, mainly due to the heterogeneity of the samples tested. For vascular activity, sweet potato, betel, cashew, maman, mint, oil palm frond, semambu, bird chili, and papaya extracts showed more than 50% relaxing effects in Wistar Kyoto rat's isolated aortic ring preparation. Most of the relaxing effects were endothelium-dependent with nitric oxide as the main mediator. Prostacyclin and endothelium-derived hyperpolarizing factors (EDHF) effects were also observed in small amounts. For the smaller vessels, mesenteric arteries, the extent of relaxation is reduced, where only oil palm frond, betel and lemongrass extracts showed more than 50% relaxing effect. It is observed that in the smaller vessel, the EDHFs effects are more prominent, especially in the betel and lemongrass extracts. Oil palm frond was selected for the in vivo study for its high phenolic content and high vascular relaxing activities in both blood vessel preparations. This study showed that oil palm frond supplementation in the diets of hypercholesterolemic rabbits led to a delayed increment in serum total cholesterol levels. There was no significant antioxidant and toxicity effect on liver, kidney and muscle observed. This study shows that most of the selected plants possess a high antioxidant and vascular relaxing activities. Antioxidants in food are important in minimizing food deterioration i.e. rancidity which affect the taste and textures of food containing lipids. In human, dietary antioxidants help to reduce oxidative stress, which is associated with the etiology of several chronic diseases such as hypertension, cancer, aging diseases, atherosclerosis and coronary artery diseases. Similarly, consumption of plants possessing vascular relaxing activities may restore and/or improve vascular functions and hence protect against vascular diseases such as hypertension

Protection of deoxyribose and DNA from degradation by using aqueous extracts of several wild plants

BACKGROUND: Aqueous extracts of 48 herbal plants were obtained via alternative extraction protocols, and were assayed for their capacity to protect deoxyribose and DNA itself from degradation (or, conversely, for their capacity to promote DNA degradation), using electrophoresis as analytical tool. RESULTS: For a given (constant) volume of extract, deoxyribose protection ranged from 14.13 ± 1.35% (mean ± SD) inhibition by dwarf mallow powder infusion, up to 106.51 ± 15.93% inhibition by avocado powder infusion. DNA protection was tested at two extract concentrations, and was slightly greater at the higher concentration. Pro-oxidant effects were essentially absent. CONCLUSION: The anti-oxidative roles of plants upon deoxyribose and DNA displayed by our experimental results were rather promising with regards to practical applications of those plants, viz. as ingredients in the formulation of nutraceutical beverages and/or foods

Antispasmodic and vasodilator activities of Morinda citrifolia root extract are mediated through blockade of voltage dependent calcium channels

<p>Abstract</p> <p>Background</p> <p><it>Morinda citrifolia </it>(Noni) is an edible plant with wide range of medicinal uses. It occurs exclusively in tropical climate zone from India through Southeast Asia and Australia to Eastern Polynesia and Hawaii. The objective of this study was to explore the possible mode(s) of action for its antispasmodic, vasodilator and cardio-suppressant effects to rationalize its medicinal use in gut and cardiovascular disorders.</p> <p>Methods</p> <p>Isolated tissue preparations such as, rabbit jejunum, rat and rabbit aorta and guinea pig atria were used to test the antispasmodic and cardiovascular relaxant effects and the possible mode of action(s) of the 70% aqueous-ethanolic extract of <it>Morinda citrifolia </it>roots (Mc.Cr).</p> <p>Results</p> <p>The Mc.Cr produced a concentration-dependent relaxation of spontaneous and high K⁺induced contractions in isolated rabbit jejunum preparations. It also caused right ward shift in the concentration response curves of Ca⁺⁺, similar to that of verapamil. In guinea-pig right atria, Mc.Cr caused inhibition of both atrial force and rate of spontaneous contractions. In rabbit thoracic aortic preparations, Mc.Cr also suppressed contractions induced by phenylephrine (1.0 μM) in normal- Ca⁺⁺and Ca⁺⁺-free Kerb's solutions and by high K⁺, similar to that of verapamil. In rat thoracic aortic preparations, Mc.Cr also relaxed the phenylephrine (1.0 μM)-induced contractions. The vasodilatory responses were not altered in the presence of L-NAME (0.1 mM) or atropine (1.0 μM) and removal of endothelium.</p> <p>Conclusions</p> <p>These results suggest that the spasmolytic and vasodilator effects of Mc.Cr root extract are mediated possibly through blockade of voltage-dependent calcium channels and release of intracellular calcium, which may explain the medicinal use of <it>Morinda citrifolia </it>in diarrhea and hypertension. However, more detailed studies are required to assess the safety and efficacy of this plant.</p

Inhibition of low-density lipoprotein oxidation and up-regulation of low-density lipoprotein receptor in HepG2 cells by tropical plant extracts

Twelve edible plant extracts rich in polyphenols were screened for their potential to inhibit oxidation of low-density lipoprotein (LDL) in vitro and to modulate LDL receptor (LDLr) activity in cultured HepG2 cells. The antioxidant activity (inhibition of LDL oxidation) was determined by measuring the formation of conjugated dienes (lag time) and thiobarbituric acid reagent substances (TBARS). Betel leaf (94%), cashew shoot (63%), Japanese mint (52%), semambu leaf (50%), palm frond (41%), sweet potato shoot, chilli fruit, papaya shoot, roselle calyx, and maman showed significantly increased lag time (>55 min, P < 0.05) and inhibition of TBARS formation (P < 0.05) compared to control. LDLr was significantly up-regulated (P < 0.05) by Japanese mint (67%), semambu (51%), cashew (50%), and noni (49%). Except for noni and betel leaf, most plant extracts studied demonstrated a positive association between antioxidant activity and the ability to up-regulate LDL receptor. Findings suggest that reported protective actions of plant polyphenols on lipoprotein metabolism might be exerted at different biochemical mechanisms.Mohd. Nizar Salleh, Irine Runnie, Paul D. Roach, Suhaila Mohamed and Mahinda Y. Abeywarden

Vasorelaxation induced by common edible tropical plant extracts in isolated rat aorta and mesenteric vascular bed

In this study, the vasodilatory actions of nine edible tropical plant extracts were investigated. Ipomoea batatas (sweet potato leaf), Piper betle (betel leaf), Anacardium occidentale (cashew leaf), Gynandropsis gynandra (maman leaf), Carica papaya (papaya leaf), and Mentha arvensis (mint leaf) extracts exhibited more than 50% relaxing effect on aortic ring preparations, while Piper betle and Cymbopogon citratus (lemongrass stalk) showed comparable vasorelaxation on isolated perfused mesenteric artery preparation. The vascular effect on the aortic ring preparations were mainly endothelium-dependent, and mediated by nitric oxide (NO) as supported by the inhibition of action in the presence of Nω-nitro-l-arginine (NOLA), an nitric oxide synthase (NOS) inhibitor, or by the removal of endothelium. In contrast, vasodilatory actions in resistance vessels (perfused mesenteric vascular beds) appear to involve several biochemical mediators, including NO, prostanoids, and endothelium-dependent hyperpolarizing factors (EDHFs). Total phenolic contents and antioxidant capacities varied among different extracts and found to be independent of vascular relaxation effects. This study demonstrates that many edible plants common in Asian diets to possess potential health benefits, affording protection at the vascular endothelium level.I Runnie, M.N Salleh, S Mohamed, R.J Head and M.Y Abeywardenahttp://www.elsevier.com/wps/find/journaldescription.cws_home/506035/description#descriptio

Polyphenol-enriched extract of oil palm fronds (Elaeis guineensis) promotes vascular relaxation via endothelium-dependent mechanisms

Article first published online: 19 DEC 2002Plant-based polyphenolic compounds have been reported to possess cardiovascular health benefits. Several dietary sources, including herbs and spices, fruits and vegetables, and tea and wine, contain an array of biologically active compounds that have been shown to be effective in retarding oxidation of low-density lipoproteins (LDL) and promoting vascular relaxation. In the present study four different plant sources, both edible and non-edible, were evaluated for potential activity. Organic extracts enriched in polyphenols were prepared from palm fronds (Elaesis guineensis); lemongrass (Cymbopogon citrates); papaya shoots (Carica papaya) and green chilli (Capsicum frutescenes) and tested for their ability to prevent in vitro oxidation of LDL, and for potential vascular relaxation actions. Rings of rat thoracic aorta and isolated perfused mesenteric vascular beds were mounted in organ baths, contracted using a half-maximal dose of noradrenaline and exposed to cumulative additions of test extracts. Palm frond extract resulted in considerable relaxation (>75%) in both preparations and was found to be endothelium-dependent as removal of endothelium or inhibition of endogenous nitric oxide (NO) led to a total loss in relaxant activity. Lemongrass extract caused a greater relaxation action in the mesenteric preparation compared to aortic rings, and appears to be mediated via NO-independent and non-prostanoid mechanisms. Of the extracts tested, palm fronds also demonstrated the highest antioxidant capacity, as determined by the ferric reducing activity/potential assay, and resulted in a significant delay (P < 0.05) in the oxidation of LDL. Collectively, these preliminary findings lend further support to the potential cardiovascular actions of plant polyphenols and also identify oil palm fronds as containing constituents that promote vascular relaxation via endothelium-dependent mechanismsMahinda Abeywardena, Irine Runnie, Mohd Nizar, Suhaila Momamed and Richard Hea

Screening Sarawak Caves for urease producing bacterial strains and evaluating their efficiency in calcium carbonate precipitation

Microbially induced calcite precipitation (MICP) is a naturally occurring biological process that has emerged as an attractive alternative ground improvement technique in Geotechnical and Civil engineering for soil strengthening and stabilization. MICP utilizes urease producing bacteria (such as Sporosarcina pastuerii, formally known as bacillus pastuerii) to catalyse the hydrolysis of urea for the production of ammonium and carbonate ions, which react with calcium ions (e.g. calcium chloride) to form calcium carbonate (calcite) that binds soil particles together, therefore increasing soil shear strength and stiffness. This study aimed at isolating urease producing bacteria from Sarawak limestone caves with the potential of precipitating calcite. A total of 28 bacterial strains were isolated from the enriched medium. Out of these isolates, 2 bacterial strains were selected based on their quick urease production. Their urease activities were assayed through changes in conductivity while their specific urease activity were calculated as the amount of urease activity per unit biomass