Three new isoflavanones (1-3) and thirteen known compounds (4-16) were isolated from the roots of Mucuna pruriens. The absolute configurations of isoflavanones 1-3 and parvisoflavanone (4), lespedeol C (5), and uncinanone C (6) were addressed by a circular dichroism technique. Isoflavanones, isoflavones, and pterocarpans of M. pruriens were found to be α-glucosidase inhibitors. Medicarpin (7) and parvisoflavone B (9) were potent α-glucosidase inhibitors (twofold less active than the standard drug acarbose). The production of bioactive metabolites in M. pruriens seems to be season-dependent.
As our global climate warms, people, and economies utilizing water resources sourced by snow and ice melt in mountain areas are disproportionately affected relative to locations that rely on rainfall. Worldwide, the vast majority of those impacted by snowfall changing to rainfall and earlier melt from a warming climate live in Asia. The Brahmaputra River originates in the declining glaciers and snowfields of the Chinese and Bhutanese Himalaya before flowing to the mega population centers of the Bangladesh delta. Bhutan's economy relies on water resource-dependent hydropower and agriculture imposing important questions about the impact of climate change on the long-term viability of water supplies in these important economic sectors. To clarify potential effects on water supplies in a warming world, and specifically to quantify the role of meltwater to river discharge in the headwaters of the Brahmaputra basin, we utilize a combined field observation-remote sensing approach to quantify river discharge source waters in a representative headwater basin, the Chamkhar Chhu. Using 4 years of water isotope and chemistry data together with a Bayesian Monte Carlo mixing model run seasonally in 2016, we find that the Chamkhar Chhu is mostly a rain-dominated basin at the lower elevation of our study domain (2591 m a.s.l.), with peak contributions from snowmelt in the early-monsoon and ice melt in the post-monsoon seasons. The radioactive tritium isotope shows glacier ice at the terminus was formed before the 1960s bomb spike while groundwater and river water samples taken in August (late monsoon) are sourced from mostly newer water inputs that show little tritium. The influence of the highly reacted Tsampa tributary, sourced by a debris covered glacier, and additional groundwater inputs generally increase major ion concentrations with distance from the glacier snout. An overall decreasing trend in the minimum snow and ice cover extent maps produced using MODIS Terra data from 2000 to 2017
Hydrologic processes that control river flow in Bhutan's Chamkhar Chhu basin are important for understanding water supply vulnerability to downstream populations in a changing climate. Seasonal source waters and flow paths of streamflow of the basin were determined using isotopic and geochemical tracers for water year 2016. Samples including surface water, groundwater, glacier meltwater, and precipitation were collected in premonsoon, monsoon, and postmonsoon seasons along an elevation transect from 2,538 to 5,158 m. Solute trends in surface waters demonstrate the major influence that tributaries can have on main stem hydrochemistry and the increasingly important role of groundwater below 3,500 m. Groundwater's role in flow is supported by a two-component hydrograph separation using SO 4 2− as a tracer and shows that groundwater is especially important to river flow in the premonsoon. Source waters to river flow were calculated using δ 18 O as a tracer, indicating that rain and meltwater are more evenly important across the elevation transect in the early monsoon period than in the postmonsoon period when ice melt contributions rapidly wane with distance from the glacier.
Springs are important water sources for domestic and agricultural uses in eastern Himalayas. This study describes the water quality scenario and major geochemical processes of the springs utilized for drinking in Kanglung locality, Bhutan. Water samples were collected at 2 end-user taps and 3 spring sources from October 2020 through April 2021 for laboratory analyses. Water samples analyzed met the WHO drinking water quality standard except for turbidity and thermotolerant coliform in some samples. The Water Quality Index values of the spring water ranged from 5.75 to 41.64, majority falling under excellent class demonstrating potability of springs tapped. The order of anion and cation chemistry were HCO3− >Cl− >SO42−, and Na+ >Ca2+>Mg2+>K+, respectively. The scatter diagrams and molar ratios of major ions indicated silicate and carbonate weathering controlling the spring water chemistry. The piper diagram indicated that springs are predominantly Ca-Mg-Cl and Na-Cl types. Gibbs diagrams inferred that spring chemistry is mainly controlled by rainwater followed by water-rock interaction. Statistical analyses indicated different sources of dissolved ions including carbonate and silicate weathering, atmospheric precipitation, dissolution of sulphate minerals, and oxidation of sulphides.
Mountain streams/springs are the primary irrigation water resource in Bhutan Himalaya, besides supporting drinking and other domestic needs. Successful crop production implies an adequate supply of high-quality irrigation water, among other factors. Thus, this study was conducted to assess the suitability of spring-fed streamwater for irrigation use and evaluate hydrogeochemical processes that regulate streamwater chemistry at the Manthong village in Kanglung, Bhutan. The water samples were analyzed for temperature, pH, EC, turbidity, TDS and major ions. Piper and Durov diagrams indicated that most samples are of the intermediate type and simple dissolution or linear mixing is the primary hydrochemical process regulating streamwater chemistry. All the measured physicochemical parameters were within the acceptable thresholds of the FAO guidelines recommended for agriculture use. Analytical results of the streamwater water quality indices, including EC, %Na%, RSBC, SAR, KR and PI, revealed its suitability for irrigation use except for MH. The IWQI results confirmed that the WS-1 has no restriction as irrigation water; however, WS-2 falls under the high restriction category. The findings of this study will serve as the baseline data and guide irrigation water management and sustainable irrigation development in the region.
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