Browsing by Author "Mandal, P."

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Open Access
In-vitro free radical scavenging activities of the leaves of Malva verticillara L
(University of North Bengal, 2012-03) Chhetri, P.K.; Mandal, P.
Antioxidants act as major defense against radical-mediated toxicity by protecting against the damages caused by free-radicals. Research on herbal products are increasingly focused on their effects on scavenging of different newly generated free-radical species and associated oxidative stress mediated complications on human health, but there are unexpectedly few studies evaluating the bioactivity of edible leafy vegetables of North Bengal, India. The purpose of the present study was to investigate the in vitro antioxidant potential of methanol extract and aqueous decoction of Malva verticillata L. [MV] leaves, consumed by local people of North Bengal. Extracts of leaves were analyzed for in vitro free radical scavenging capacity, the total phenol and flavonoid content and preliminary phytochemical analysis. The antioxidant property was estimated using reducing power, superoxide radical scavenging activity and DPPH assays. Methanol extract of leaves were found to be effective in DPPH and superoxide radical scavenging activity when compared with aqueous decoction of MV. Overall strong correlation between the mean values of total phenol content and IC50 values of DPPH and superoxide free radical scavenging capacity was observed. Principle Component Analysis (PCA) indicated that phenolic functional groups and reducing potential of methanol and aqueous extracts were mostly contributed for their antioxidant capacity. The present study revealed that methanol extract of the leaves of MV comprise effective source of natural antioxidants, which might be helpful in preventing the progress of various oxidative stress induced diseases.
Open Access
Influence of culture media and environmental factors on mycelial growth, sporulation and spore germination behaviour of Curvularia eragrostidis (P. Hennings) Mayer
(University of North Bengal, 2008-03) Saha, A.; Dasgupta, S.; Mandal, P.; Saha, D.
Curvularia eragrostidis is a foliar fungal pathogen of young tea plants. It causes leaf spot disease of tea. Mycelial growth, sporulation and spore germination behaviour of the pathogen were studied. Six different media were tested for mycelial growth. Among these, potato carrot agar (PCA) was found best for the mycelial growth and sporulation. Maximum mycelial growth was attained after 15 days of incubation. Mycelial growth was also studied in different temperatures and pH. Optimum temperature of growth was 25 °C and best growth was obtained at pH 6.0. Glucose and peptone were best carbon and nitrogen sources respectively for growth and sporulation of the fungus. The optimum conditions of spore germination were found to be at pH 7.25 and at incubation temperature of 25 °C. Keywords: Sporulation; Curvularia eragrostidis; Mycelial growth, fungus
Open Access
Nitric oxide and calcium signalling in plants under salinity stress and their crosstalk - A Review
(University of North Bengal, 2016-03) Gupta, S.K.; Mandal, P.
Salinity is considered as one of the major factor affecting the crop production throughout the world. The oxidative stress induced by salinity can retard plant growth and yield as major part of energy is wasted on conserving water and improving ionic balance. The free radicals produced during stress are considered to be a major factor for most of the damages as these free radicals attack vital biomolecules such as lipids, protein and carbohydrates which are the basic requirements of almost all physiological and developmental processes. Understanding the mechanism of stress tolerance along with the involvement of important signalling molecules in stress signalling network is essential for crop improvement. Likewise, the two signalling molecules nitric oxide and calcium ion have been reported to be actively involved in upregulation of various stress response mechanism thus indicating the existence of a possible cross talk among these molecules and other associated pathways. In this review, emphasis was given on the impact of salinity and oxidative stress mediated damages on plant system. Additionally, the role of nitric oxide and calcium ion as signalling molecules in response to stress signals and their implication in mitigation of salinity stress has also been discussed.
Open Access
Variation of antioxidant properties and phytochemical constituents of tea cultivated under various agronomic conditions at Terai region of North Bengal
(University of North Bengal, 2008-03) Misra, T.K.; Saha, A.; Nanda, A.K.; Mandal, P.
The studies were conducted during 2007-2008 in three cultivars of tea (Camellia sinensis) namely, TV26, TV29 and Dangri Manipuri Jat, at tea estates of Terai, North Bengal. Commercial standard plucked tea leaves were assayed to determine antioxidants activity and related phytochemical constituents. DPPH was used to determine the antioxidant properties of bud+leaf (B+L), bud+two leaves (B+2L), bud+three leaves (B+3L) and matured leaves (L). Subsequently, total phenolics, flavonols and hydrolysable tannins were estimated using standard methods. The result showed that free-radicals scavenging potentiality and chemical composition varies significantly at different growing conditions and leaf maturation. Statistical analysis showed significant relation between antioxidant and some phytochemical composition of dry tea leaves, among which phenolics (R2 =0.904, P< 0.001), tannins (R2= 0.567, P< 0.05) and flavonols (R2= 0.314, P< 0.05) bear significant correlation. Soil physicochemical parameters like pH (R2=0.537, P< 0.05), nitrogen (R2=0.618, P< 0.01), K2O (R2=0.106, insignificant), P2O5 (R=0.730, P< 0.01), S (R2=0.157, insignificant) and soil moisture (R2=0.745, P< 0.01) influence free-radical scavenging activity in tea leaves. Antioxidant quality of tea varies with maturation stages of leaves and the pattern is specific for a selected varietes. From our observation it may be concluded that antioxidant quality is dependent on some fertility parameters of soil and maturation of leaf. These results suggests that appropriate agronomic practices and proper choice of plucking may help to preserve the tea antioxidant quality.