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

Abstract

Plant-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 mechanisms.

Phenolic Compounds and Antioxidant Potential of Nigerian Red Palm Oil (Elaeis Guineensis)

“…Other studies demonstrate that ferulic acids alleviates lipid peroxidation in diabetic rats, synergistically interact with other antioxidants to preserve physiological integrity of cells exposed to free radicals (Mathew and Abraham, 2004;Graf, 1992;Anselmi, 2004) and attenuates the processes that drive the pathology associated with Alzheimer's disease if the treatment is initiated before the neuroinflammatory processes can develop. In addition, ferulic acid protects against hydroxyl and peroxyl radical oxidation in synaptosomal and neuronal cell culture systems, as well as strongly inhibits arylamine N-acetyltransferase activities in human gastrointestinal microflora (Mathew and Abraham 2004;Graf, 1992;Anselmi, 2004) In conclusion, palm oil contains a rich mixture of phenolic compounds with potent antioxidant and radical scavenging activity to suggest that the widely reported capacity of palm oil to modulate the effect of oxidative stress on serum and antioxidant enzymes in membranes of liver and kidney, oxidative stress hypertension, suppress pre-neoplastic mammary epithelial cell proliferation, inhibit diesel-exhaust induced lung tumorigenesis, inhibit tumour promotion as well as modulate the immune system (Wattanapenpaiboon and Wahlqvist, 2003;Edem, 2002;Elson,1992;Sundram et al, 2003;Abeywardena et al, 2002;Balasundram et al, 2003;Yun et al, 2008) cannot be ascribed to their carotenoids and tocopherol components alone, but also to their antioxidant polyphenol contents. 祃 Methanol Extract (10g/2.5ml) Figure 2.…”

“…The fruit also contains components such as carotenoids (alpha, beta, and gamma carotenes), vitamin E (tocophoreols and tocotrienols), sterols (sitosterol, stigmasterol and campesterol), phospholipids, glycolipids and squalene, which are of known nutritional and health benefits (Wattanapenpaiboon and Wahlqvist, 2003;Manorama and Rukmini (1991). In addition, it has been reported that certain powerful water-soluble antioxidants, phenolic acids and flavonoids can be recovered from the palm oil mill effluents (Abeywardena et al, 2002;Balasundram et al, 2003;Yun et al, 2008).…”

ANTIOXIDANT ACTIVITIES OF Elaeis guineensis LEAVES

“…Some researchers also discovered oil palm leaves have potential health benefits. Abeywardena et al (2002) disclosed a polyphenol-enriched extract derived from Elaeis guineensis leaf. They reported that the said extract can be used to promote vascular relaxation via endothelium-dependent mechanisms.…”

Antioxidant Research in Asia in the Period from 2000-2008

“…Common banana Musaceae Flower Antioxidant [139][140][141] Psidium guajava L. Guava Myrtaceae Fruit Antioxidant [142,143] Capsicum frutescens L. Bird chili Solanaceae Fruit Antioxidant, LDLr [99,100,104,107,112] modulation effects and vasorelaxation properties Lycium chinense Mill.…”

“…African oil palm Arecaceae Frond Antioxidant, [104,107] vasorelaxation properties and LDLr* modulation effects Var. radiata plant NO** inhibitory Diplazium esculentum Swartz Vegetable fern Athyriaceae Shoot Antioxidant [99,100,108,109] (Retzius) Brassica alboglabra Bailey Chinese kale Brassicaceae leaves Antioxidant [99,100,110] Brassica oleracea L. Cauliflower, Broccoli, Cabbage Brassicaceae Flower leaves Antioxidant [100] and Chinese cabbage Raphanus sativus L.…”