Citation
Ismail Suhaimy, Noor Wahida
(2016)
Gastroprotective activity of semi-purified (partitions)
Methanolic leaf extract of melastoma malabathricum l.
(senduduk.
Masters thesis, Universiti Putra Malaysia.
Abstract
Melastoma malabathricum L. (Melastomaceae) is traditionally used by the Malays to
treat gastric ulcer and this claim was supported by the gastroprotective activity
observed with methanolic extract of M. malabtahricum leaves (MEMM). The present
study aimed to determine the gastroprotective activity of the methanolic crude extract
of Melastoma malabathricum (MEMM) by semi-purified extract (partitions) using
solvents of different polarities. The study began with screening the potential acute
toxicity of MEMM before it was partitioned using different solvents. The petroleum
ether partition (PEMM) was non-polar, ethyl acetate partition (EAMM) was
intermediate polar and aqueous extract (AQMM) was polar. Next, we screened their
phytochemical compounds followed by evaluation of their in vitro antioxidant
activities using total phenolic content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH),
superoxide dismutase (SOD) and oxygen radical absorbance capacity (ORAC) assays
and screened their in vitro anti-inflammatory activities using xanthine oxidase (XO)
and lipoxygenase (LOX) assays. All partitions were investigated for possible
gastroprotective activity against ethanol-induced gastric ulcer. Rats (n = 6) received
10% dimethyl sulfoxide (DMSO, negative control), 100 mg ranitidine (positive
control) or semi-purified extract (50, 250, 500 mg/kg) orally once daily for 7 days
followed by ulcer induction using absolute ethanol (1 mL/200 gm). The gastric tissues
were collected for macroscopic and microscopic examination to determine the most
effective partition. The most effective partition was selected for studied their antisecretory
activity by using a pylorus ligation model to determine the gastric juice
volume, pH, free and total acidity, and mucus content. The selected partition
progressed to the next stage of the study, to determine the antioxidant enzyme activity
(SOD, catalase [CAT], glutathione [GSH], thiobarbituric acid–reactive substances
[TBARS]) and cytoprotective activity (prostaglandin E2 [PGE2]) in gastric tissues. The
effective dose of the partition was investigated to determine the possible involvement
of endogenous nitric oxide (NO) and sulfhydryl (SH) compounds in the
gastroprotective effects. Finally, the compounds responsible for gastroprotection in the
effective partition were identified. Result showed phytochemical screening of PEMM, EAMM and AQMM revealed the presence of saponins, flavonoids, triterpenes, tannins
and polyphenolic, but not alkaloids. In the in vitro antioxidant assay, i) EAMM showed
high TPC content compared to PEMM and AQMM, ii) all partitions showed high
scavenging activity in the SOD assay; EAMM and AQMM showed better results as
compared to PEMM in the iii) DPPH and iv) ORAC assays. In the in vitro antiinflammatory
assay, the partitions had low activity in the XO assay while EAMM and
AQMM had moderate and low activity, respectively, in the LOX assay. All partitions
exerted significant (p < 0.05) gastroprotection against ethanol-induced gastric ulcer in
the following order: EAMM > AQMM > PEMM. EAMM was the most effective
partition as proven via its mechanisms of action: i) anti-secretory activity as shown by
the reduction of gastric juice volume, free and total acidity as well as increased pH and
gastric wall mucus, ii) antioxidant enzyme activity as shown by the increased SOD,
CAT, GSH and decreased malondialdehyde (MDA) in gastric tissues, iii)
cytoprotective activity as shown by the increased PGE2 levels in gastric tissue. The
gastroprotective activity involved NO and SH compounds, as shown by the partition
being ineffective in iv) assay when N-omega-nitro-L-arginine methyl ester (L-NAME;
a NO blocker) and v) N-ethylmaleimide (NEM; a SH blocker) were used. In
conclusion, EAMM showed better in vitro antioxidant and antiinflammatory activity
partly attributed to its gastroprotective activity demonstrated via the mechanisms of
action of its anti-secretory, antioxidant and cytoprotective activity that depend on the
presence of NO and SH. The presence of flavonoids-based compounds and
hydrocinnamic acid compounds which might act synergistically was believed to
contribute to this gastroprotective activity.
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