Pushpa S. Murthy

Synthesis and quorum sensing inhibitory activity of key phenolic compounds of ginger and their derivatives

Phenolic components of ginger (Zingiber officinale Roscoe) viz. [6]-gingerol, [6]-shogaol and zingerone exhibited quorum sensing inhibitory activity (QSI) against Chromobacterium violaceum and Pseudomonas aeruginosa. The inhibitory activity of all the compounds was studied by zone inhibition, pyocyanin, and violacein assay. All the compounds displayed good inhibition at 500ppm. [6]-Azashogaol, a new derivative of [6]-shogaol has been synthesized by Beckmann rearrangement of its oxime in the presence of ZnCl2. The structure elucidation of this new derivative was carried out by 1D ((1)H NMR and (13)C NMR) and 2D-NMR (COSY, HSQC and NOESY) spectral studies. This compound showed good QSI activity against P. aeruginosa. An isoxazoline derivative of [6]-gingerol was prepared and it exhibited good QSI activity. Present study illustrated that, the phenolic compounds of ginger and their derivatives form a class of compounds with promising QSI activity.

In vitro antifungal activity of dehydrozingerone and its fungitoxic properties.

UNLABELLED The efficacy of Dehydrozingerone (DZ; dehydroderivative of zingerone) as an antifungal agent and its mode of action against food spoilage fungal pathogens was studied and presented. DZ is a constituent of ginger (Zingiber officinale rhizomes) and structural half analogue of curcumin. Its efficacy against Aspergillus oryzae, Aspergillus flavus, Aspergillus niger, Aspergillus ochraceus, Fusarium oxysporum and Penicillium chrysogenum was evaluated. Effect of DZ on the growth and sporulation of A. ochraceus was also studied. The fungal species were susceptible to DZ and the minimum inhibitory concentration and fungicidal concentration ranged from 755 to 911 μM and 880 to 1041 μM respectively. The mycelial and spore germination was significantly inhibited; reduction in the weight of the cell mass, carbohydrate, protein, DNA and RNA constituents in the cells isolated from cultures of A. ochraceus grown with DZ were observed. Scanning electron microscopy studies revealed morphological observations such as cell lysis, inhibition and morphological alterations in hyphae and sporulation in A. ochraceus on treatment with DZ. PRACTICAL APPLICATION Current investigations revealed that DZ is a potential antifungal agent and can find application as an additive or adjuvant in food and pharmaceutical industries after appropriate toxicological studies.

Synthesis and antibacterial properties of 2,3-dideoxyglucosides of terpene alcohols and phenols.

Essential oils and their oxygenated terpene constituents possess potent antimicrobial properties. In the present study, a facile synthetic route to the 2,3-dideoxy 1-O-glucosides of important phenols and terpene alcohols in excellent yields (85-96%) has been delineated. Studies on their antimicrobial action against four food-borne pathogens--Bacillus cereus, Staphylococcus aureus, Escherichia coli and Yersinia enterocolitica--demonstrated that the zone of inhibition, in general, was higher for the 2,3-unsaturated 1-O-glucoside derivatives (1b-6b) and the corresponding saturated glucosides (1c-5c) when compared to the parent alcohols/phenols (1-6). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values for these derivatives too were generally lower than those of the parent compounds. Furthermore, the time-kill and bacteriolysis assays too demonstrated the greater antimicrobial potential of the derivatives. The 2,3-dideoxy 1-O-glucosides of phenols and terpene alcohols were more effective in their antimicrobial action than the corresponding parent compounds. The study indicated that these novel derivatives can find useful application in control of food-related pathogenic microbes in foods.

2,3-Dideoxyglucosides of selected terpene phenols and alcohols as potent antifungal compounds.

The antifungal activities of novel 2,3-unsaturated and 2,3-dideoxy 1-O-glucosides of carvacrol, thymol, and perillyl alcohol were tested against Aspergillus flavus, Aspergillus ochraceus, Fusarium oxysporum, Saccharomyces cerevisiae and Candida albicans. In the agar well diffusion tests, zones of inhibition for the derivatives of carvacrol, thymol and perillyl alcohol were higher (15-30mm) in the case of filamentous fungi than those for the parent compounds. Their MIC and MFC values indicated that the 2,3-unsaturated and 2,3-dideoxy 1-O-glucosides of carvacrol and thymol exhibited more fungicidal activity than the other compounds. Further, the 2,3-dideoxyglucosides of carvacrol and thymol, exhibited antitoxigenic effects against A. ochraceus and A. flavus and inhibited the production of ochratoxin and aflatoxin-B2. Propidium iodide influx assay demonstrated the lysis of C. albicans cells by carvacrol and its 2,3-unsaturated 1-O-glucoside and the loss of the membrane integrity. These new 2,3-dideoxyglucosides can be useful as antifungal agents and condiments in foods.

Structure-function activity of dehydrozingerone and its derivatives as antioxidant and antimicrobial compounds

Dehydrozingerone, structural half analogue of curcumin, is a phenolic compound isolated from ginger (Zingiber officinale) rhizomes. Dehydrozingerone and several of its derivatives such as glucopyranosides and its tetra acetate derivative and 4-O-acetyl and methyl derivatives of dehydrozingerone were synthesized in the present study. Dehydrozingerone, synthesised with improved yield was used for the synthesis of Dehydrozingerone 4-O-β-D-glucopyranoside (first time report) by modified Koenigs-Knorr-Zemplén method. Structures of all the compounds have been established using spectroscopic methods. These compounds were tested for radical scavenging activity by DPPH and FRAP method as well as for antibacterial and antifungal activities. The parent molecule exhibited better scavenging activity as compared to its derivatives indicating the significance of free phenolic hydroxyl group. Also, Dehydrozingerone and its derivatives exhibited antibacterial as well as antifungal activity due to the conjugation system present, which includes α,β-unsaturated carbonyl (C = O) group. This study gave an insight into structural requirements for dehydrozingerone activity.

In-vitro Mycological activity of essential oil from Zingiber zerumbet rhizomes.

Abstract The volatile oil (1.12%) from the Z. zerumbet rhizomes were extracted using Clevenger’s distillation. The GC and GC-MS profile of the Z. zerumbet volatiles revealed several components of which Zerumbone was the principal compound (49.8%) followed by α-Caryophyllene (20.1%) and trace of other compounds. The antifungal property of volatiles was studied against Aspergillus flavus and Aspergillus ochraceus. The fungal species were susceptible to volatiles, and the minimum fungicidal concentration (MFC) was 160 ppm for A. flavus and 175 ppm for A. ochraceus.The studies with the food toxigenic organisms treated with volatiles were significant. It revealed substantial inhibition of mycelia, spore germination, reduction in biomass, carbohydrate, protein, chitin and genetic constituents. The inhibitory action of zerumbet volatile oil on A. flavus and A. ochraceus involves cell wall damage and distortion in the metabolism. The SEM of A. flavus and A .ocharceus illustrates that treatment with the oil leads to distortion of hyphae and the absence of conidiophores. The Z. zerumbet volatiles (100 ppm) were found to be antimycotoxin on maize as food substrates and were dose-dependent on confirmation by HPLC. Z. zerumbet oil is potentially useful as biopreservative because of its antifungal and antimycotoxin efficacy.

Enzyme Immobilization Methods and Applications in the Food Industry

Abstract Enzymes are biological catalysts that play an immense role in the food industry. However, the desirable characteristics of enzymes are hindered by their long-term operational stability, shelf storage life, recovery, and reuse. These drawbacks can be overcome by enzyme immobilization, which enhances the functional efficiency and reproducibility while requiring less labor input and reducing contamination. Therefore, this boosts the stability of the products. The primary immobilization of the enzyme was amino cyclase of Aspergillus oryzae for the production of L-amino acids from Japan. Key enzymes such as pectinase and cellulases are immobilized on suitable carriers and are useful in the food industry (baking, dairy products, jams, and jellies), beverage processing (wine, beer, fruit, and vegetable juices), etc. There are various techniques to immobilize an enzyme, including adsorption (static process, dynamic process, reactor loading, electrodeposition), Covalent bonding (diazoation, peptide bond polyfunctional reagents), entrapment (inclusion in the gels, fibers, and microcapsules), and copolymerization and encapsulation (microencapsulation, nanoencapsulation). Nanotechnology is one of the most promising fields that attempts to provide an efficient technique that could answer several challenges in terms of economy and industrial development in food processing.