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Lu, Yao (2016) Melodinus eugeniifolius. (apocynaceae juss.): a phytochemical and pharmacological study. PhD thesis, University of Nottingham.

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Abstract

Melodinus eugeniifolius. a very rare medicinal plant belongs to the family of Apocynaceae. This family consists of 424 genera and 1,500 species of trees. In the Asia-Pacific region, about 20 species of Apocynaceae are used to treat various diseases like cancer, cardiovascular diseases and infectious diseases. Furthermore, almost no pharmacological and phytochemical studies in genera Melodinus, no pharmacological and phytochemical studies in this plant as well. This study was undertaken to screen the phytochemical and phytochemical aspects on the plant Melodinus eugeniifolius.

Qualitative phytochemical analysis of the crude extract was determined for the presence of tannins, flavonoids, alkaloids, saponins and sterols. Phytochemical analysis of Melodinus eugeniifolius. revealed presence of alkaloids, cardiac glycosides, sterols, steroids and flavonoids in crude extracts of leaves and barks. The crude extracts of the plant were subjected to several biological assays and were then focused on anticancer aspect.

Bacterial infections have been known to generate extensive formation of free radicals which is becoming increasingly recognized in the pathogenesis of the many human diseases. Melodinus eugeniifolius leaves and barks were screened for the antibacterial activities, among the different extracts tested, all the extracts displayed remarkable antibacterial activity against Staphylococcus aureus, Bacillus cereus and Escherichia coli.

The role of free radicals and active oxygen is becoming increasingly recognized in the pathogenesis of the many human diseases, including cancer, neurodegenerative diseases, ageing, and atherosclerosis. The FRAP assay (Ferric reducing antioxidant power), DPPH radical scavenging assay (1,1-diphenyl-2-picryl hydrazyl radical reducing power methods), and β-carotene bleaching assays were employed to determine the radical scavenging activity of the plant extracts using 96-well microtiter plate. Percentage decolourisation was plotted against the concentration of the sample and the EC50 values were determined. Vitamin C (l-ascorbic acid), Gallic Acid and Quercetin were used as positive control. Ethanol extracts showed significant antioxidant activity. In this test, the ethanol extract of leaves and barks exhibited profound antioxidant activities. The EC50 (μg/mL) for the ethanol extract of barks was as good as Gallic acid.

Plant substances continue to serve as a wellspring of drugs for the world population and several plant-based drugs are in extensive clinical use. Preliminary antiparasitic screening of six extracts of Melodinus eugeniifolius leaves and barks were screened for their in vitro antileishmanial and antitumor activities, among the different extracts tested, the ethanol and hexane extract of barks showed significant antileishmanial activities.

Cancers remain the leading cause of death worldwide and the search for novel anti-cancer agents from medicinal plants has become crucial. Infections and free radical generation are recognized in the pathogenesis of cancer. Six different extractions of Melodinus eugeniifolius leaves and barks were screened for their in vitro antitumor activities, among the different extracts tested, the chloroform extracts of barks and leaves showed significant antitumor activities and would not damage the normal cells. According to the current result, susceptible cell lines were found to be the HT-29 human colon cancer cell line, HCT-116 human colon cancer cell line, MCF-7 human breast cancer cell line, Caco-2 human colon adenocarcinoma cell line, HK-1 human nasopharyngeal cancer cell line, and MRC-5 human lung fibroblast cell line.

Results from our phytochemical analysis revealed that the chloroform extract of leaves and barks of Melodinus eugeniifolius accumulate substantial amounts of alkaloids and cardiac glycosides which could be well correlated with the activities measured.



Bioassay guided isolation and nine chemical compounds were isolated by column chromatography fractions and were identified by NMR techniques. Five indole alkaloids were isolated and were identified as yohimbine hydrochloride, tabersonine, yohimbine, β-yohimbine, and leuconolam respectively. The new alkaloid, having a pentacyclic diazaspiro system, was named Melodinoid. Other constituents identified were epigallocatechin and loganic acid. Some of the compounds isolated from the plant were subjected to biological assays and were then focused on anti-cancer aspect.

Alkaloids always present significant anticancer capacity. Three alkaloids isolated from Melodinus eugeniifolius were screened by MTT assays against two cancer cells and a normal cell. All the compounds revealed significant anticancer capacity on the two human cancer cell lines, and not damage the normal cells.

Hence, further research on the mechanism of some of the isolated compounds with target pharmacological activities, relative in vivo anticancer tests, and even clinical trials are recommended to ascertain the efficacy, safety and other mechanisms of action to application in the pharmaceutical industry as natural therapeutic agents.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Wiart, Christophe Khoo, Teng Jin
Keywords:	melodinus eugeniifolius, medical plant, apocynaceae, cardiovascular diseases, cancer, pharmacological
Subjects:	R Medicine > RC Internal medicine
Faculties/Schools:	University of Nottingham, Malaysia > Faculty of Science and Engineering — Science > School of Pharmacy
Item ID:	30428
Depositing User:	YAO, LU
Date Deposited:	22 Apr 2020 15:49
Last Modified:	06 May 2020 08:32
URI:	https://eprints.nottingham.ac.uk/id/eprint/30428

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