Lekha Nath Khanal

Dr. Lekha Nath Khanal

Department of Chemistry, Tribhuvan University, Kathmandu, Bāgmatī, Nepal
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Research Focus & Metrics

Academic Career Length

5Years (2022-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 January 2022 in Journal of Nanomaterials
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Journal Article
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LKLekha Nath Khanal
Lekha Nath Khanal
KSKhaga Raj Sharma
Khaga Raj Sharma
HPHari Paudyal
Hari Paudyal
KPKshama Parajuli
Kshama Parajuli
BDBipeen Dahal
Bipeen Dahal
SKSurya Kant Kalauni
Surya Kant Kalauni
The fabrication of metal nanoparticles through green synthetic pathways using plant extracts has increased attention due to low cost, benevolent methods, fewer hazardous byproducts, and applications. Silver nanoparticles (AgNPs) were synthesized by reacting to aqueous root extracts of Rubus ellipticus Sm. (RERE) with AgNO3 solution (1 mM) at an ambient condition. The visual change of color from light yellow to reddish brown and the absorption peak at 416‐420 nm in the UV‐visible spectra indicated the formation of AgNPs in the solution. The shifting of the positions in the FTIR spectra indicated the potential role of the functional groups as capping and stabilizing agents. The powder XRD diffractogram exposed the crystalline nature of the nanoparticles. The surface morphology and the elemental composition of the AgNPs were established by the FESEM and EDX analysis. The TEM images revealed the spherical and monodispersed nanoparticles of size ranging from 13.85 to 34.30 nm with an average of 25.20 ± 7.01 nm (n = 10). The biogenic AgNPs showed a better 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging activity with lower IC50 (13.83 ± 0.33 μg/mL) as compared to that of the RERE with IC50 (15.86 ± 4.14 μg/mL). The synthesized AgNPs showed higher zones of inhibition (ZOI) on the agar well diffusion method against Enterococcus faecalis (ATCC 29212), Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923), and Klebsiella pneumoniae (ATCC 700603). The result of this study highlights the potential benefits of R. ellipticus root extract‐based AgNPs for biomedical practices.

26 March 2022 in The Scientific World Journal
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LKLekha Nath Khanal
Lekha Nath Khanal
KSKhaga Raj Sharma
Khaga Raj Sharma
YPYuba Raj Pokharel
Yuba Raj Pokharel
SKSurya Kant Kalauni
Surya Kant Kalauni
Plants have long been considered as a basis of medicines for different indigenous cultures around the globe. They continue as a prominent source of important phytoconstituents which exhibit significant biological activities. In this study, we performed the phytochemical screening, estimation of total phenolic and flavonoids, antioxidants, and antimicrobial activities of the stem bark of Beilschmiedia roxburghiana Nees using different solvents. The total phenolic and total flavonoid contents ranged from 106.73±1.62mg GAE/g and 99.32±0.66mg QE/g (methanol extract) to 65.59±1.79mg GAE/g and 29.98±0.90mg QE/g (n-hexane extract), respectively. The maximum 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity with a half-maximal inhibitory concentration (IC50) of 39.86±3.69μg/mL was observed for methanol extract followed by aqueous (IC50=43.55±6.16μg/mL), ethyl acetate (IC50=44.30±5.88μg/mL), dichloromethane (IC50=71.50±4.70μg/mL), and the lowest activity was observed for n-hexane extract. The disc diffusion method revealed that the ethyl acetate extract exhibited relatively higher activity against Salmonella typhi (ZOI=13mm), and moderate activities against Shigella sonnei, Acinetobacter baumannii, Klebsiella pneumoniae, and Staphylococcus aureus (ZOI=12mm). The methanol and aqueous extracts showed nearly parallel and the n-hexane and dichloromethane extracts exhibited mild antibacterial activities. The results indicated that the polarity index of the extracting solvents amplified the biological activities of the extract. The study is helpful to support the validity of the traditional application of the plant as natural medicine.

20 June 2023 in Inorganics
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LKLekha Nath Khanal
Lekha Nath Khanal
PDPurna Prasad Dhakal
Purna Prasad Dhakal
MKMani Ram Kandel
Mani Ram Kandel
Debendra AcharyaDebendra Acharya
Debendra Acharya
Ek Raj BaralEk Raj Baral
Ek Raj Baral
SKSurya Kant Kalauni
Surya Kant Kalauni
The investigation of using medicinal plants for the production and application of silver nanoparticles (AgNPs) has attracted growing research interest. In this study, AgNPs are synthesized from the stem barks of the Pyrus pashia medicinal plant using a biosynthetic strategy. The reaction conditions were optimized under ambient conditions, including concentration, temperature, time, and pH, and various techniques were employed, such as UV-visible, FTIR, XRD, FESEM, and TEM, to characterize the synthesized AgNPs. The AgNPs produced through this biosynthesis method were found to be spherical and polydispersed, with an average size of 23.92 ± 7.04 nm. The synthesized AgNPs demonstrated an enhanced DPPH free radical scavenging capacity compared to the aqueous extract, with IC50 values of 10.67 ± 0.05 µg/mL and 13.66 ± 0.35 µg/mL, respectively. In the agar well diffusion method, the synthesized AgNPs showed higher antibacterial activity than that of the extract against Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATCC 29212), Salmonella typhi (ATCC 14028), and Shigella sonnei (ATCC 25931). Based on these findings, the study suggests that green synthesized AgNPs from P. pashia could be used for biomedical applications.

13 February 2025 in Chemengineering
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KPKshama Parajuli
Kshama Parajuli
LKLekha Nath Khanal
Lekha Nath Khanal
GCGanga Gharty Chhetri
Ganga Gharty Chhetri
SKSamjhana Koju
Samjhana Koju
SBShushan Bhujel
Shushan Bhujel
Bhoj Raj PoudelBhoj Raj Poudel
Bhoj Raj Poudel
Plant-based preparation of nanomaterials has become a recent global research focus due to its cost-effectiveness, sustainability, and environmentally friendly approach. This study aims to synthesize silver nanoparticles (HAgNPs) using red lentil husk aqueous extract (LHE) and to assess its antibacterial activity. Synthesized HAgNPs were analyzed by ultraviolet-visible spectroscopy (UV-vis.), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray (EDX) analysis. The antibacterial efficacy of synthesized HAgNPs was investigated against Staphylococcus aureus (ATCC No: 25923), Enterococcus faecalis (ATCC No: 29212), Klebsiella pneumoniae (ATCC No: 700603), and Shigella sonnei (ATCC No: 25931) at varying concentrations via the agar well diffusion scheme. The UV-vis absorption maximum observed around 420 nm directed the creation of HAgNPs. The shifting of peak positions in the FTIR spectrum of the synthesized HAgNPs compared to the FTIR spectrum peak positions of LHE indicated the involvement of biomolecules present in LHE in reducing silver ions to metallic silver. XRD examination of the prepared sample suggested face-centred cubic crystals of the HAgNPs. The average particle dimension of prepared HAgNPs was 8.9 nm by the Debye–Scherer equation. An FESEM examination of the synthesized HAgNPs revealed spherical morphology, while the EDX study showed that silver (Ag0) was the predominant component, comprising 62.3% by weight. The synthesized HAgNPs displayed a higher DPPH radical scavenging capacity (IC50 = 38.87 ± 3.52 µg/mL) than that of LHE (IC50 = 65.27 ± 1.17 µg/mL). The prepared HAgNPs exhibited significant antibacterial efficacy against some human pathogen bacteria at lower concentrations. Hence, the present study highlights an environmentally benevolent and economical synthetic approach to the preparation of HAgNPs and its potential utility for the production of biomedical products.

1 July 2022 in Journal of Institute of Science and Technology
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LKLekha Nath Khanal
Lekha Nath Khanal
KSKhaga Raj Sharma
Khaga Raj Sharma
YPYuba Raj Pokharel
Yuba Raj Pokharel
SKSurya Kant Kalauni
Surya Kant Kalauni
The northern areas of Nepal are rich in biodiversity and contain a large number of medicinal plant species including the Genus Ephedra of evergreen gymnosperm, belonging to the family Ephedraceae. The plants have been used by the peoples of the Himalayan region for the treatment of asthma, blood pressure, and gastritis for many years. This study was aimed for the evaluation of phytochemical, antioxidant, and antimicrobial activities of methanol, ethyl acetate, dichloromethane, and n-hexane extracts, and gas chromatography-mass spectrometry (GCMS) profiling of the essential oil of the aerial parts of Ephedra pachyclada Boiss from Mustang district of Nepal. Antioxidant activity was evaluated by 2,2-dipheny-1-picrylhydrazyl (DPPH) free radical scavenging assay and antimicrobial activity by the agar well diffusion method. Total phenolics and total flavonoid content were determined by Folin-Ciocalteu and aluminum chloride colorimetric method, respectively. The methanol extract contained the highest total phenolic content of 54.42 ± 1.40 mg GAE/g followed by the ethyl acetate (46.84 ± 0.62 mg GAE/g), DCM extract (19.58 ± 0.24 mg GAE/g), and the lowest TPC was shown for n-hexane extract (5.21 ± 1.40 mg GAE/g) of the dry weight. The methanol extract showed the maximum TFC of 33.28 ± 0.48 mg QE/g, followed by ethyl acetate extract (31.73 ± 0.52 mg QE/g), DCM extract (31.64 ± 0.56 mg QE/g), and the least value was obtained for the n-hexane extract (21.44 ± 2.91 mg QE/g). The methanol extract showed the highest antioxidant activity with a half-maximal inhibitory concentration (IC50) of 37.81 ± 2.24 μg/mL. The methanol extract showed potent activity against Escherichia coli (ATCC 25922), and Staphylococcus aureus (ATCC 25923) with zones of inhibition of 13 mm and 12 mm respectively. Ethyl acetate extract showed a slight potency against Staphylococcus aureus (ATCC 25923) with a zone of inhibition of 9 mm. The essential oil contained diisooctyl phthalate (46.90%), dodecane, 2,6,11-trimethyl-(16.35%), dodecane, 4,6-dimethyl- (11.59%), tetrapentacontane (11.56%), and myrtenol (4.37) as the major compounds. The plant exhibited significant antioxidant and antimicrobial activities which could be used as the source to isolate the active natural antioxidant and antimicrobial agent as the drug candidate in the future drug discovery process.

13 May 2024 in Prithvi Academic Journal
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SKSurya Kant Kalauni
Surya Kant Kalauni
JKJeetendra Karki
Jeetendra Karki
MSMenaka Sharma
Menaka Sharma
LKLekha Nath Khanal
Lekha Nath Khanal
Green tea has gained popularity among consumers in recent years due to its several health benefits. It exhibits antioxidant properties, antidiabetic effects, and helpful to reduce cholesterol, stress, and anxiety. This study aims to identify the phytochemicals and assess the antioxidant and antidiabetic capacity of methanol extracts of green tea common in Nepal. The total phenolic and flavonoid contents were evaluated by Folin-Ciocalteu and aluminum chloride colorimetric methods. The antioxidant capacity was assessed using the 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging technique, while the starch-iodine method was employed to measure the α-amylase inhibition capability. Phytochemical screening showed the abundance of alkaloids, flavonoids, polyphenols, and carbohydrates in the tea. The total phenolic and flavonoid contents were 54.20 ± 1.41mg GAE/g and 91.0.50 mg QE/g respectively. The tea extract was found to show significant antioxidant and α-amylase inhibition capacities with half-maximal concentration (IC50) values of 53.79 ± 3.93 and 66.47 ± 1.94 μg/mL respectively. The outcomes of this study ratify the advantages of green tea in the management of various health issues associated to free radicals and hyperglycemia.