Browsing by Author "Shubhra Singh"

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Chemical profile, antifungal, antiaflatoxigenic and antioxidant activity of Citrus maxima Burm. and Citrus sinensis (L.) Osbeck essential oils and their cyclic monoterpene, DL-limonene
(2010) Priyanka Singh; Ravindra Shukla; Bhanu Prakash; Ashok Kumar; Shubhra Singh; Prashant Kumar Mishra; Nawal Kishore Dubey
The study deals with antifungal, antiaflatoxigenic and antioxidant activity of Citrus maxima and Citrus sinensis essential oils (EOs) and their phytochemical composition. The EOs were obtained by hydrodistillation and their chemical profile was determined through GC and GC-MS analysis. Both the EOs and their 1:1 combination showed broad fungitoxic spectrum against different food contaminating moulds. The EOs and their combination completely inhibited aflatoxin B1 (AFB1) production at 500ppm, whereas, dl-limonene, the major component of EOs showed better antiaflatoxigenic efficacy even at 250ppm. Both the oils exhibited antioxidant activity as DPPH free radical scavenger in dose dependent manner. The IC50 for radical scavenging efficacy of C. maxima and C. sinensis oils were to be 8.84 and 9.45μlml-1, respectively. The EOs were found non-mammalian toxic showing high LD50 for mice (oral, acute). The oils may be recommended as safe plant based antimicrobials as well as antioxidants for enhancement of shelf life of food commodities by checking their fungal infestation, aflatoxin production as well as lipid peroxidation. © 2010 Elsevier Ltd.
Effect of Citrus reticulata and Cymbopogon citratus essential oils on Aspergillus flavus growth and aflatoxin production on Asparagus racemosus
(2010) Priyanka Singh; Ravindra Shukla; Ashok Kumar; Bhanu Prakash; Shubhra Singh; Nawal Kishore Dubey
Essential oils extracted from Citrus reticulata and Cymbopogon citratus were tested in vitro against the toxigenic strain of Aspergillus flavus, isolated from the tuberous roots of Asparagus racemosus, used in preparation of herbal drugs. The essential oils completely inhibited the growth of A. flavus at 750 ppm and also exhibited a broad fungitoxic spectrum against nine additional fungi isolated from the roots. Citrus reticulata and Cymbopogon citratus essential oils completely inhibited aflatoxin B1 production at 750 and 500 ppm, respectively. During in vivo investigation, the incidence of fungi and aflatoxin B1 production decreased considerably in essential oil-treated root samples. The findings thus indicate possible exploitation of the essential oils as effective inhibitor of aflatoxin B1 production and as post-harvest fungitoxicant of traditionally used plant origin for the control of storage fungi. These essential oils may be recommended as plant-based antifungals as well as aflatoxin B1 suppressors in post-harvest processing of herbal samples. © Springer Science+Business Media B.V. 2010.
New pairs of acyl sucroses from Petunia nyctaginiflora Juss.
(Indian Chemical Society, 2004) A. Sajeli Begum; Usha Kiran Rai; Shubhra Singh; Mahendra Sahai
Four new acyl sucroses, isolated from Petunia nyctaginiflora Juss. (Solanaceae) were characterised as 2,3,4-trihexanoyl-α-D-glucopyranosyl- β-D-fructofuranoside, 2,3,4-triheptanoyl-α-D-glucopyranosyl-β-D- fructofuranoside, 2,3,4-trihexanoyl-α-D-glucopyranosyl-β-D-6-acetyl fructofuranoside, 2,3,4-triheptanoyl-α-D-glucopyranosyl-β-D-6-acetyl fructofuranoside, on the basis of chemical and spectroscopic evidence.
Squamocin-O1 and squamocin-O2, new adjacent bis-tetrahydrofuran acetogenins from the seeds of Annona squamosa
(2002) Hiroshi Araya; Mahendra Sahai; Shubhra Singh; Ajit Kumar Singh; Mitsuzi Yoshida; Noriyuki Hara; Yoshinori Fujimoto
Two bis-tetrahydrofuran acetogenins, squamocin-O1 (1) and squamocin-O2 (2), were isolated from a MeOH extract of seeds of Annona squamosa L. Their structures were determined by spectral means including precursor-ion scanning mass spectral analysis for their aminal derivatives. The configurations at the oxymethine chiral centers were assigned as 12R, 15R, 16R, 19R, 20R, 23R, 24S, 28S, 36S for 1 and 12S, 15R, 16R, 19R, 20R, 23R, 24S, 28S, 36S for 2, based on 1H NMR analysis of their Mosher's ester derivatives and CD data, © 2002 Elsevier Science Ltd. All rights reserved.