Tricyclic Sesquiterpenes FromVetiveria zizanoides(L.) Nash as Antimycobacterial Agents

Vetiver, Vetiveria zizanioides (L.) Nash: Biotechnology, Biorefineries, and the Production of Volatile Phytochemicals

This current review study covers the applications of vetiver essential oil (VEO) in phytoremediation, emphasizing its remedial capabilities in the cleaning of environmental pollutants like pesticides, fertilizers, fungicides, herbicides, heavy metals, dyes, and other industrial wastes such as chemical, mining, pharmaceutical, and other radioactive wastes. The review also emphasizes the pharmacological potential of vetiver essential oil for different applications, such as antioxidant, anti-inflammatory, antifungal, antibacterial, antitubercular, antihyperglycemic, antidepressant, hepatoprotective, and nephroprotective uses. The commercial potential of vetiver essential oil in diverse sectors, including global perspectives, is also illustrated along with demand scenarios in different sectors like food, beverage, fragrance, cosmetic and aromatherapy, hygiene, and pharmaceutical sectors. The main constituents of vetiver oil, their relative proportion, and the key findings of pharmacological studies performed using VEOs or their constituents are also summarized in this review article, with special emphasis on activity against phytopathogens.

Synergistic Antibacterial Activity of Gallic Acid Based Chalcone Indl 2 by Inhibiting Efflux Pump Transporters

As a part of novel discovery of drugs from natural resources, present study was undertaken to explore the antibacterial potential of chalcone Indl-2 in combination with different group of antibiotics. MIC of antibiotics was reduced up to eight folds against the different cultures of E. coli by both chalcones. Among the two compounds, the i. e. 1-(3', 4,'5'-trimethoxyphenyl)-3-(3-Indyl)-prop-2-enone (6, Indl-2), a chalcone derivative of gallic acid (Indl-2) was better along with tetracycline (TET) worked synergistically and was found to inhibit efflux transporters as obvious by ethidium bromide efflux confirmed by ATPase assays and docking studies. In combination, Indl-2 kills the MDREC-KG4 cells, post-antibiotic effect (PAE) of TET was prolonged and mutant prevention concentration (MPC) of TET was also decreased. In-vivo studies revealed that Indl-2 reduces the concentration of TNF-α. In acute oral toxicity study, Indl-2 was non-toxic and well tolerated up-to dose of 2000 mg/kg. Perhaps, the study is going to report gallic acid derived chalcone as synergistic agent acting via inhibiting the primary efflux pumps.

Analysis of cell death in Bacillus subtilis caused by sesquiterpenes from Chrysopogon zizanioides (L.) Roberty

Recently, the antibacterial effects of essential oils have been investigated in addition to their therapeutic purposes. Owing to their hydrophobic nature, they are thought to perturb the integrity of the bacterial cell membrane, leading to cell death. Against such antibiotic challenges, bacteria develop mechanisms for cell envelope stress responses (CESR). In Bacillus subtilis, a gram-positive sporulating soil bacterium, the extracytoplasmic function (ECF) sigma factor-mediated response system plays a pivotal role in CESR. Among them, σ^M is strongly involved in response to cell envelope stress, including a shortage of available bactoprenol. Vetiver essential oil, a product of Chrysopogon zizanioides (L.) Roberty root, is also known to possess bactericidal activity. σ^M was exclusively and strongly induced when the cells were exposed to Vetiver extract, and depletion of multi-ECF sigma factors (ΔsigM, ΔsigW, ΔsigX, and ΔsigV) enhanced sensitivity to it. From this quadruple mutant strain, the suppressor strains, which restored resistance to the bactericidal activity of Vetiver extract, emerged, although attempts to obtain resistant strains from the wild type did not succeed. Whole-genome resequencing of the suppressor strains and genetic analysis revealed inactivation of xseB or pnpA, which code for exodeoxyribonuclease or polynucleotide phosphorylase, respectively. This allowed the quadruple mutant strain to escape from cell death caused by Vetiver extract. Composition analysis suggested that the sesquiterpene, khusimol, might contribute to the bactericidal activity of the Vetiver extract.

Nephroprotective activity of Vetiveria zizanioides (L.) Nash supplement in doxorubicin-induced nephrotoxicity model of Wistar rats

The nephroprotective effect of standardized aqueous root extract of Vetiveria zizanioides (L.) Nash (Family: Poaceae) was investigated in doxorubicin-induced (20 mg/kg, ip) experimental nephrotoxicity model of Wistar rats. The freeze-dried aqueous refluxed (4 hr) root extract of V. zizanioides (25, 50; equivalent human therapeutic dose and 100 mg/kg) was administered separately to nephrotoxic Wistar rats (n = 6/group). Supplement of V. zizanioides resulted a dose-dependent reduction in raised serum creatinine, β₂ -microglobulin, and blood urea nitrogen and a subsequent increase in serum total protein and albumin in nephrotoxic rats (p < .05). An attenuation of the doxorubicin-induced features of renal parenchymal injury was observed on H- and E-stained sections of the kidney tissues. Nootkatone, dehydroaromadendrene, isokhusenic acid, α-vetivone, and isolongifolene were identified in the methanol extract of V. zizanioides based on the GC-MS chromatogram analysis. The findings revealed that the supplement of standardized aqueous root extract of V. zizanioides had a significant dose-dependent nephroprotective activity against doxorubicin-induced experimental nephrotoxicity. PRACTICAL APPLICATIONS: Vetiveria zizanioides is a medicinal plant with a variety of therapeutic applications in kidney-related diseases. Apparently, it is used as a food ingredient due to its fresh and elegant scent and potential bioactivities. The aqueous root extract of V. zizanioides exerted relatively high antioxidant potential in vitro, substantiating the health effects of the plant pertaining to kidney diseases as a potential source of dietary antioxidant. The administration of the plant extract resulted in significant nephroprotection against doxorubicin-induced experimental nephrotoxicity revealing the significance of V. zizanioides as a promising dietary supplement in the management of kidney disease.

Natural products against key Mycobacterium tuberculosis enzymatic targets: Emerging opportunities for drug discovery

For centuries, natural products (NPs) have served as powerful therapeutics against a variety of human ailments. Nowadays, they still represent invaluable resources for the treatment of many diseases, including bacterial infections. After nearly three decades since the World Health Organization's (WHO) declaration of tuberculosis (TB) as a global health emergency, Mycobacterium tuberculosis (Mtb) continues to claim millions of lives, remaining among the leading causes of death worldwide. In the last years, several efforts have been devoted to shortening and improving treatment outcomes, and to overcoming the increasing resistance phenomenon. Nature has always provided a virtually unlimited source of bioactive molecules, which have inspired the development of new drugs. NPs are characterized by an exceptional chemical and structural diversity, the result of millennia of evolutionary responses to various stimuli. Thanks to their favorable structural features and their enzymatic origin, they are naturally prone to bind proteins and exhibit bioactivities. Furthermore, their worldwide distribution and ease of accessibility has contributed to promote investigations on their activity. Overall, these characteristics make NPs excellent models for the design of novel therapeutics. This review offers a critical and comprehensive overview of the most promising NPs, isolated from plants, fungi, marine species, and bacteria, endowed with inhibitory properties against traditional and emerging mycobacterial enzymatic targets. A selection of 86 compounds is here discussed, with a special emphasis on their biological activity, structure-activity relationships, and mechanism of action. Our study corroborates the antimycobacterial potential of NPs, substantiating their relevance in future drug discovery and development efforts.

Phytochemical Screening, Antioxidant Assay and Cytotoxic Profile for Different Extracts of Chrysopogon zizanioides Roots

The Chrysopogon zizanioides plant possesses multiple traditional uses, especially in therapeutics, but only a few articles have reported its biological activity. Hence, the present study was planned to explore the phytochemical constituents, cytotoxic potential, radical scavenging activity, and GC/MS (Gas chromatography & Mass spectrometry) analysis of the vetiver root extracts. The roots extracted with different solvents exhibited more significant phytochemical constituents in polar solvents in comparison to non-polar ones, favoring the extraction of a greater number of components in highly polar solvents. All the extracts were tested for their cytotoxicity using SRB (Sulforhodamine B) assay. They confirmed ethanolic extract as a potent extract with GI₅₀ 56±0.5 μg/ml in oral cancer (SCC-29B) along with no cytotoxicity in healthy cells (Vero cells), making it a safer therapeutic option in comparison to standard Adriamycin. This extract was also analyzed for its antioxidant potential by DPPH (1,1-Diphenyl-2-picrylhydrazyl) assay with IC₅₀ value 10.73 μg/ml, which was quite comparable to Ascorbic acid having IC₅₀ value 4.61 μg/ml. The quantitative analysis of ethanolic extract exhibited 107 compounds amongst which Khusenic acid, Ascorbic acid, Junipen, gamma-Himachalene, alpha-Guaiene were the majorly occurring compounds that can be explored further for their cytotoxic activity.

Brevifoliol and its Analogs: A New Class of Anti-tubercular Agents

Brevifoliol is an abeo-taxane isolated from the Taxus wallichiana needles; eighteen semisynthetic esters derivatives of brevifoliol were prepared by Steglich esterification and screened for their anti-tubercular potential against Mycobacterium tuberculosis H37Ra avirulent strain. The 3- [chloro (7)] and 3, 5-[dinitro (8)] benzoic acid ester derivatives were most active (MIC 25 ug/ml) against the pathogen. Further, in silico docking studies of the active derivative 7 with mycobacterium enzyme inhA (enoyl-ACP reductase) gave the LibDock score of 152.68 and binding energy of -208.62 and formed three hydrogen bonds with SER94, MET98, and SER94. Similarly, when derivative 8 docked with inhA, it gave the LibDock score of 113.55 and binding energy of -175.46 and formed a single hydrogen bond with GLN100 and Pi-interaction with PHE97. On the other hand, the known standard drug isoniazid (INH) gave the LibDock score of 61.63, binding energy of -81.25 and formed one hydrogen bond with ASP148. These molecular docking results and the way of binding pattern indicated that compounds 7 and 8 bound well within the binding pocket of inhA and showed a higher binding affinity than the known drug isoniazid. Additionally, both the derivatives (7 and 8) showed no cytotoxicity, with CC50 195.10 and 111.36, respectively towards the mouse bone marrow-derived macrophages.

Comparative Drug Resistance Reversal Potential of Natural Glycosides: Potential of Synergy Niaziridin & Niazirin

Background:

Due to the limited availability of antibiotics, Gram-negative bacteria (GNB) acquire different levels of drug resistance. It raised an urgent need to identify such agents, which can reverse the phenomenon of drug resistance.

Objective:

To understand the mechanism of drug resistance reversal of glycosides; niaziridin and niazirin isolated from the pods of Moringa oleifera and ouabain (control) against the clinical isolates of multidrug-resistant Escherichia coli.

Methods:

The MICs were determined following the CLSI guidelines for broth micro-dilution. In-vitro combination studies were performed by broth checkerboard method followed by Time-Kill studies, the efflux pump inhibition assay, ATPase inhibitory activity, mutation prevention concentration and in-silico studies.

Results:

The results showed that both glycosides did not possess antibacterial activity of their own, but in combination, they reduced the MIC of tetracycline up to 16 folds. Both were found to inhibit efflux pumps, but niaziridin was the best. In real time expression pattern analysis, niaziridin was also found responsible for the down expression of the two important efflux pump acrB & yojI genes alone as well as in combination. Niaziridin was also able to over express the porin forming genes (ompA & ompX). These glycosides decreased the mutation prevention concentration of tetracycline.

Conclusion:

This is the first ever report on glycosides, niazirin and niaziridin acting as drug resistance reversal agent through efflux pump inhibition and modulation of expression pattern drug resistant genes. This study may be helpful in preparing an effective antibacterial combination against the drug-resistant GNB from a widely growing Moringa oleifera.