Biogenic Synthesis, Characterization and Pharmacological Evaluation of Nano-Particles Prepared by Using the Extracts of Arisaema jacquemontii, Hedera nepalensis and Valeriana jatamansi

Abstract

Nanobiotechnology and green synthesis of nanoparticles (NPs) are novel and efficient alternatives for synthesis of metal NPs using extracts of medicinal plants. Arisaema jacquemontii (family: Araceae), Hedera nepalensis (family: Araliaceae) and Valariana jatamansi (family: Valerianaceae) are important medicinal plants of Himalayas and Kashmir. A. jacquemontii has anti-proliferative property and is traditionally used as snakebite antidote, ringworm killer and to treat skin diseases. Leaf juice of H. nepalensis is given in dyspepsia and leaves paste is applied on ulcers. V. jatamansi is used as tranquilliser, carminative, anti-inflammatory, expectorant and muscle relaxant. The aim of the present study was to investigate the green synthesis and characterization of nanoparticles (NPs) and pharmacological evaluation of the three plants. Methanolic extract solution (50mg/100ml de-ionized water) of selected parts of the test plants was used to synthesize gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs). Methanolic extract was mixed with gold chloride (AuCl3) solution (0.1 mM concentration) in 3:1 ratios to produce AuNPs from A. jacquemontii tuber and 4:1 ratios for AuNPs from the rest of the samples. To synthesize AgNPs from tubers, 0.1mM AgNO3 was mixed with extract at 1:5 ratios. AgNPs were formed from H. nepalensis stem and leaves at 1:5 and 1:2 ratios respectively. AgNPs of V. jatamansi root and shoot were synthesized at 1:10 and 1:5 ratios respectively. Preliminary observation of synthesis of NPs was carried out by visual detection of color change from light yellow to dark purple and dark yellow/brown for AuNPs and AgNPs synthesis respectively. UV-vis spectrophotometric analysis further confirmed the synthesis of AgNPs and AuNPs by showing SPR peak in 400-500nm and 500-600nm range respectively. Temperature and salt stability studies of AgNPs and AuNPs revealed the stability of NPs at 20-40°C temperature and at milimolar salt concentration. FTIR confirmed the involvement of mainly carboxylic acid/phenol, tertiary alcohol, alkene, alkane and alcohol of plant extracts in reduction of Au-metal to form AuNPs. XRD analysis revealed that all AuNPs were crystalline in nature and the average nanocrystallite size for AuNPs synthesized from all three test plants was in the range of 6.23nm-10.92nm. Crystals were cubic in nature. SEM analysis revealed average size of 36nm, 32nm, 29nm, 25nm and 24nm for tubers, stem, leaves, root and shoot nanosphere AuNPs. According to XRD data, synthesized AgNPs were mainly crystalline in nature. SEM results reported size of synthesized AgNPs in 30nm-49nm range. AgNPs of all the samples were spherical in shape. FTIR analysis revealed the involvement of mainly alkenes, carboxylic acids, ether and aromatic ring (aryl) groups in reduction of Ag-metal. Overall among all the tested microbes, P. aeruginosa was the most sensitive microbe (62-88% growth inhibition) followed by C. albicans (59-82% growth inhibition). The most resistant bacterium was K. pneumonia (35-47% growth inhibition). V. jatamansi showed better antimicrobial activities than the other two tested plant species. AgNPs reported greater antimicrobial activity than AuNPs. Among all the tested extracts, generally, n-butanol fractions and methanolic crude extracts showed higher antioxidant activity. NPs also reported their antioxidant potential. Phytochemical screening of extracts indicated the presence of several bioactive compounds in the extract including flavonoids, sterols, saponins, tannins, alkaloids and oils in different extracts of different parts of all the three test plant species. On the basis of these results it is evident that all the three plants can be used for stable and active NPs synthesis that posses antimicrobial and antioxidant properties. Extracts of test plants also revealed antifungal, antibacterial and antioxidant properties due to the presence of bioactive compounds in it.