Phytochemical Studies, Investigation of Anti Alzheimer and Anti-Cancer Potentials of Polygonum Hydropiper L.

Abstract

Alzheimer‟s disease (AD) is the most common neurodegenerative disorder, characterized by memory impairment, behavioral turbulence, cognitive dysfunction and imperfection in routine life activities. AD is the most common cause of dementia among people aged 65 years and older, with about 35 million sufferers worldwide. It is the fifth leading cause of death in people above 65 years of age and is predicted to affect 1 in 85 people globally by 2050. The most important pathological aspects of AD include deficiency of neurotransmitter acetylcholine, deposition of amyloid plaques (Aβ) and neurofibrillary tangles. Cancer is another life-threatening disease and serious health problem worldwide. More than half of the 20 million people diagnosed with cancer belong to the developing regions of the world. Due to the alarming increase in cancer incidences, it is estimated to have 10 million deaths annually by 2020. Natural products play a significant role in the drug discovery and development process. The main advantage of natural products as a source of lead compounds is the tremendous molecular diversity found in nature. Based on the folkloric uses of P. hydropiper and related species, we investigated solvent extracts, essential oils and isolated compounds for anti-Alzheimer's and cytotoxic potentials by using in-vitro and in-vivo models. A total of seven fractions were derived from the dried whole plant of P. hydropiper using solvent-solvent extraction method. Essential oils from leaves and flowers were also isolated and subjected to Gas Chromatography-Mass Spectrometry (GC-MS) analysis. Crude methanolic extract (Ph.Cr) was subjected to qualitative phytochemical analysis, GC-MS analysis and column chromatography for isolation of bioactive compounds. Ph.Cr was tested positive for the presence of alkaloids, flavonoids, saponins, tannins, triterpenoids anthraquinones, glycosides. In GC-MS analysis of Ph.Cr, n-hexane (Ph.Hex), chloroform (Ph.Chf), butanol (Ph.Bt) and ethyl acetate (Ph.EtAc) fractions 126, 124, 181, 131 and 164 compounds were identified respectively. In acetylcholinesterase (AChE) inhibition assay, Ph.Hex , Ph.Chf and Ph.Sp were the most potent fractions that displayed IC50 values of 35, 55 and 100 μg/ml respectively. While in butyrylcholinesterase (BChE) inhibition assay, Ph.Aq and Ph.Hex were more potent with IC50 values of 3 and 40 μg/ml respectively. In DPPH free radicals scavenging assay, Ph.Bt, Ph.Chf, Ph.EtAc, Ph.Lo and Ph.Fo fractions were more potent among all samples with IC50 of 3, 10, 15, 20 and 200 μg/ml respectively. In ABTS anti-radicals assay, Ph.Bt, Ph.EtAc, Ph.Aq, Ph.Sp revealed highest ABTS scavenging effect, thus causing IC50 values91.03, 90.65, 90.56 and 90.84% inhibition of free radicals respectively. From the most active fraction including chloroform and ethyl acetate six compounds (MA1-6) were isolated , purified and their structures were confirmed by 1H NMR, 13C NMR and mass spectra. The most potent compound MA-1 and Ph.Lo were subjected to in-vivo anti-Alzheimer and cell line studies. In AChE inhibition assay, MA-1 exhibited IC50 of 55 μg/ml, whereas, in BChE inhibitory assay MA-1 showed IC50 of 50 μg/ml. Likewise Ph.Lo and Ph.Fo demonstrated IC50's of 120 and 220 μg/ml respectively in AChE inhibition assay. In BChE inhibitory study, Ph.Lo and Ph.Fo showed IC50's of 130 and 225 μg/ml respectively. In DPPH, ABTS, H2O2 anti-radicals assays, MA-1 exhibited IC50's of 140, 120 and 280 μg/ml respectively. Whereas, Ph.Lo and Ph.Fo displayed IC50's of 180 and 45 μg/ml respectively. Moreover, the IC50's were 60 and 50 μg/ml for Ph.Lo and Ph.Fo respectively in H2O2 radicals scavenging assay. In beta amyloid cleaving enzyme (BACE1) inhibition assay, MA-1 and Ph.Lo displayed 73.00 ± 3.05 and 79.33 ± 3.17% enzyme inhibition respectively at 1 mg/ml concentration. In trasgenic animals model of Alzheimer disease MA-1 and Ph.Lo showed significant decline in cognitive dysfunctions of animals evaluated through behavioral assessment tools including Paddling water Maze (PWM), Y-Maze, open field and balance beam. Ex-vivo studies suggested that MA-1 and Ph.Lo sufficiently cross blood brain barier (BBB) and treated transgenic animals with these samples showed a significant decline in the AChE, BChE activities in the cortical and hippocampus tissues. Moreover, the cortical and hippocampus tissues of transgenic animals treated with MA-1 and Ph.Lo exhibitied a significant DPPH radicals scavenging effect. In cytotoxicity studies, Ph.Lo was less effective against all tested cell lines with LC50> 1000 μg/ml. MA-1 displayed LD50 of 440, 170, 200 μg/ml against NIH/3T3, HeLa and MCF-7 cell lines. Moreover, compound MA-3 displayed LD50 of170, 60 and 140 μg/ml against HeLA, MCF-7 and NIH/3T3 cell lines respectively. Whereas, compound MA-4 demonstrated 380, 160 and 58 140 μg/ml against HeLA, MCF-7 and NIH/3T3 cell lines respectively. Concluding the current study, it is stated that P. hydropiper crude extracts and isolated compounds possess considerable neuroprotective and selective cytotoxic potentials. Further studies are required regarding their potential use in Alzheimer disease and cancer.