Natural and synthetic chromenes, fused chromenes, and versatility of dihydrobenzo[h]chromenes in organic synthesis.

Soil microbial biomass is an important component of soil organic matter constituting from 2 to 5% of the soil organic carbon and play a significant role in the cycling of nutrients and overall organic matter dynamics. The present study assessed the effects of three forest types (Banj-oak forest, Chir-pine forest and Mixed oak-pine forest) on the soil physico-chemical properties and microbial biomass Carbon in Central Himalaya, India. The soil microbial biomass carbon was determined by chloroform fumigation extraction method. In the 2 year of study period, the soil microbial biomass carbon (Cmic) was significantly higher in Mixed oak-pine forest (681 ± 1.81–763 ± 1.82 μg g−1) than in the Banj-oak (518 ± 1.50–576 ± 1.73 μg g−1) and Chir-pine forest (418 ± 1.42–507 ± 2.05 μg g−1). Though insignificant, all the forest types showed distinct seasonal variations in microbial biomass carbon with a minimum value in winter season and maximum value in rainy season. The soil microbial quotients (Cmic to Corg) were higher in Chir-pine (2.52–4.18) and Banj-oak forest (2.26–4.02) than those reported in Mixed oak-pine forest (1.44–2.24). These results indicate that Mixed oak-pine forest is better in sustaining the soil microbial biomass and soil nutrients than Banj-oak and Chir-pine forest. It recommends that nutrients rich Mixed oak-pine forest should be preferred as a forest management practice to promote microbial diversity, their activities and soil quality enhancement in Central Himalayan forests.

Effect of vegetation type and season on microbial biomass carbon in Central Himalayan forest soils, India

In Central Himalaya, anthropogenic activities have led to the widespread replacement of Banj oak (Quercus leucotrichophora) forest by Chir pine (Pinus roxburghii) for decades. This study was conducted to determine how natural Banj oak, Chir pine, and mixed oak-pine forest would differ in soil microbial biomass and soil nutrients. Soil microbial biomass nitrogen (SMBN) and phosphorus (SMBP), soil organic carbon (SOC) total nitrogen (TN), and total phosphorus (TP) in the 0 to 15 cm soil layer were investigated in the Central Himalayan region in the stands of Banj oak, mixed oak-pine, and Chir pine forest. The SMBN and SMBP were significantly higher in Banj oak and mixed oak-pine forest as compared to Chir pine forest. The ratios of SMBN to TN (SMBN/TN) and SMBP to TP (SMBP/TP) were significantly higher in the Chir pine forest, indicating that in this forest, the proportion of microbial biomass N and P to total soil N and P was higher as compared to Banj oak forest. A similar pattern of variation was found in relation to season across the forests, all with an apparent peak in the rainy season. These results indicate that low microbial biomass N and P may be one of the reasons to create a nutrient poor site in Chir pine forest. The collection of pine litter by local people also impairs the return of nutrients to the soil and makes it difficult for Banj oak to re-invade areas occupied by Chir pine. This calls for cautions in large-scale conversions of the Banj oak forests to coniferous plantations as a forest management practice on concerns of sustaining soil productivity.

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Changes in soil biochemical properties following replacement of Banj oak forest with Chir pine in Central Himalaya, India

The chemistry and biology of bicoumarins

Objective
To investigate antibacterial potential of Trifolium alexandrinum (T. alexandrinum) Linn. against seven gram positive and eleven gram negative hospital isolated human pathogenic bacterial strains responsible for many tropical diseases.

Antibacterial activity of leaves extracts of Trifolium alexandrinum Linn. against pathogenic bacteria causing tropical diseases

In this study, the impact of cropping systems on physicochemical properties of soil and microbial biomass was evaluated. Soil was collected from four cultivated fields (cropland, crop + single tree species, crop + multiple tree species and homegardens) and one uncultivated (agriculturally discarded) field and analysed. The outcome of the present study indicated that cultivated land squandered about 14% C and 5% N in 8 years of cultivation to the nearby uncultivated land. Soil microbial biomass of cultivated land with multiple tree species (C + mT) was greater than other systems and showed an appreciable seasonal variation. The microbial biomass carbon (Cmic) assorted from 166 to 266 μg g and microbial biomass nitrogen (Nmic) from 11 to 41 μg g. Cmic contributed 1.25–1.90% of soil C and Nmic 0.83– 3.77% of soil N. Among cultivated land, maximum Cmic and Nmic were reported in C + mT system which suggested that tree plantation in cultivated land has significant positive effects on microbial biomass and other soil properties by shifting natural soil properties under the similar environmental circumstances.

Microbial Biomass Carbon and Nitrogen in Relation to Cropping Systems in Central Himalaya, India

Various organic and aqueous extracts of aerial part of Boenninghausenia albiflora (Rutaceae) obtained by infusion and maceration were screened for their antimicrobial activity against eight animal and plant pathogenic bacteria (Bacillus subtilis, Staphylococcus aureus, Erwinia chrysanthemi, Escherichia coli, Proteus vulgaris, Xanthomonas phaseoli, Agrobacterium tumefaciens and Xanthomonas campestris) using disc diffusion method. Out of total 32 tests performed, 27 tests showed positive antibacterial activity at 1000 mg/ml concentration, whereas 15 instances exhibited zone of inhibition ³ 10 mm at same concentration. The activity shown by some of the extracts was found higher than ampicillin (10 mcg) and erythromycin (15 mcg), standard antibiotic used.

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Antibacterial activity of Boenninghausenia albiflora Reichb. (Rutaceae).

Antibacterial Evaluation of the Himalayan Medicinal Plant Valeriana wallichii DC. (Valerianaceae)

Phytochemical profiling, antioxidant and antibacterial efficacy of a native Himalayan Fern: Woodwardia unigemmata (Makino) Nakai.

The antibacterial property of methanol, ethanol and hexane extracts of Berberis aristata, Chenopodium ambrosioides and Tinospora cordifolia grown in Kumaun Himalayan were investigated against some pathogenic gram positive and gram negative bacterial strains (Bacillus subtilis, Agrobacterium tumefaciens, Escherichia coli, Xanthomonas phaseoli and Erwinia chrysanthemi) using disc diffusion method. Methanol extract of B. aristata was found with highest inhibitory activity against E. chrysanthemi (ZOI, 11±0.3mm). Whereas lowest inhibition was recorded in ethanolic extract of B. aristata against E. coli. The hexane extract of B. aristata and methanolic extract of C. ambrosioides were found totally inactive against all the pathogens tested.

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K. Khulbe

Papers

Microbial Biomass Carbon and Nitrogen in Relation to Cropping Systems in Central Himalaya, India

Antibacterial activity of Boenninghausenia albiflora Reichb. (Rutaceae).

Antibacterial Evaluation of the Himalayan Medicinal Plant Valeriana wallichii DC. (Valerianaceae)

Phytochemical profiling, antioxidant and antibacterial efficacy of a native Himalayan Fern: Woodwardia unigemmata (Makino) Nakai.

Antibacterial activity of three medicinal plants of kumaun himalaya against some pathogenic bacteria