Mohan B. Gewali

Constituents of the latex of Euphorbia antiquorum

From the latex of Euphorbia antiquorum, three new triterpenes, euphol 3-O-cinnamate, antiquol A and antiquol B, together with known triterpenes, euphol, 24-methylenecycloartanol and cycloeucalenol, were isolated. (Z)-9-Nonacosene, sitosterol and p-acetoxyphenol were also isolated from the latex.

An antiproliferative norditerpene dilactone, Nagilactone C, from Podocarpus neriifolius.

An ethanolic extract of Podocarpus neriifolius D. Don (Podocarpaceae) showed antiproliferative activity against two major tumor cell lines, viz. human HT-1080 fibrosarcoma and murine color 26-L5 carcinoma. Bioassay guided fractionation showed the highest antiproliferative activity in chloroform-soluble fraction. Nagilactone C, the major constituent of this fraction was isolated and characterized by using NMR, IR and FAB-MS spectroscopic methods. Nagilactone C possessed potent antiproliferative activity against human fibrosarcoma and murine colon carcinoma tumor cell lines exhibiting ED50 values of 2.3 and 1.2 microg/ml, respectively. Hence, nagilactone C could be the active constituent present in this plant.

Two phenolic glycosides from Curculigo orchioides Gaertn.

One new glycoside derivative from syringic acid and one new phenol glycoside, curculigoside E (1) and orchioside D (2), were isolated and characterized from the rootstock of Curculigo orchioides collected in the Nawalparasi District (Nepal). The structures of the new isolated compounds were elucidated by means of spectroscopic methods such as 1D, 2D NMR and MS.

Novel cycloartane triterpenoids from the Nepal native plant Caragana sukiensis.

A phytochemical study on the arial part of Caragana sukiensis resulted in the isolation of three new cycloartane triterpenoids 1-3 and their structures were fully established on the basis of detailed spectroscopic (especially 2D NMR and Mass) analysis. These new compounds possessed hemiacetal fused tetrahydropyran rings at C-15/C-16, while 2 and 3 also contains d-xylose moiety.

The Scenario of Carbonaceous Aerosols and Total Solar Radiation in Two Cities in Nepal

Measurement of elemental carbon (EC) and black carbon (BC) aerosols was carried out using AE-31, 7 channel aethalometer at Kathmandu and Biratnagar; two mega cities of Nepal, for five months, January to May 2011 to study its temporal and spatial variation. Total solar radiation was also monitored using Kipp and Zonen CMP 6 pyranometer. Monthly concentration variation for EC and BC was distinct in both study sites. At Biratnagar, monthly EC concentration varies from 3.3 -20.7 µg /m 3 while in Kathmandu it varies between 6.0-13.7 µg /m 3 . Similarly, BC monthly concentration ranges from 3.3 -20.1 µg /m 3 and 7.0-14.9 µg /m 3 respectively. It was found that both EC and BC were highest during January in both the sites and it decreases gradually. Monthly average solar radiation shows a maximum value in May and minimum in January. A distinct anti-correlation between monthly average carbonaceous aerosols and total solar radiation was observed. Moreover, there was a pronounced diurnal variation of both carbonaceous aerosols EC and BC in the sites with two high peaks one in the morning at about 9:00 and another at late evening 20:00 local time with minimum concentration in the afternoon. The nature of peaks were different at two sites. Biratnagar shows a larger evening peak while Kathmandu shows in the morning inferring heavy domestic and industrial fuel consuming activities in evening and morning respectively. In addition to this, daily and monthly concentration of EC was more than BC at Biratnagar reflecting slightly more biomass fuel consumption than fossil fuel for domestic, industrial and other urban activities. In contrast to this, Kathmandu shows more domination of fossil fuel than biofuel because of reverse order concentration of carbonaceous aerosols. Total solar radiation also shows apparent diurnal variation in both sites with the highest value at around noon time.