Mushroom mediated selective bioreduction of S-(+)-carvone to cis-(-)-dihydrocarvone: approach towards a safer biocatalysis.

Dihydrocarvone, possessing four stereoisomers is an important flavour and chiral building block in chemical synthesis. Ascomycetes are well known for the selective bioreduction of carvone to dihydrocarvone. Often, these fungi produce mycotoxins which may contaminate the biocatalytic product. Herein, Ganoderma sessile, a polypore mushroom, selectively reduced S-(+)-carvone to cis-(-)-dihydrocarvone (DHC) in its submerged culture. In an optimised condition (0.75 g/L, 18 h, pH 3-5, 30 °C and 150 rpm), 82.7% cis-(-)-DHC was obtained in gas chromatography-mass spectrometry profile of the fermented product. The absolute titre of cis-(-)-DHC in fermentation medium was 0.35 ± 0.01 g/L. However, substrate toxicity (IC50 0.15 g/L) drastically reduced the transformation at higher carvone concentration (≥1.0 g/L). On the other hand, R-(-)-carvone was less selective and efficient in producing the desired isomer i.e. trans-(+)-DHC. G. sessile is the member of a group of non-toxic medicinal mushrooms and may be a safer yet efficient option for producing cis-(-)-DHC biocatalytically.

A high performance thin layer chromatography (HPTLC) method for the quality assessment of citronella oil: application in commercial sample analysis.

Citronella oil, extracted from Cymbopogon species (winterianus and nardus) is a commercially valuable essential oil used in personal-care products and insect repellents. Routine analysis in gas chromatography is incapable of detecting high-boiling adulterants therein. In this study, an HPTLC technique was developed for the absolute quantification of citronellal (characteristic chemical marker) and triglyceride (main constituent of vegetable oil adulterant) in citronella oil for its quality assessment. It was validated in terms of specificity, linearity, sensitivity, accuracy and precision. Further, the developed method was employed to quantify citronellal and triglyceride in twenty commercial samples. The results showed a wide variation in citronellal content (trace to 30.65% w/w) and could differentiate its two chemotypes. Also, it revealed the possibility of vegetable oil adulteration through the detection and quantification of triglyceride in selected samples. It can be a simple and rapid technique for the quality control of citronella oil.

Chavibetol: major and potent phytotoxin in betel (Piper betle L.) leaf essential oil.

BACKGROUND: Many essential oils and their constituent volatile organic compounds are known to be phytotoxic and potential bioherbicides. This study aims to investigate the phytotoxicity of propenylbenzene-rich essential oils and identify active molecule(s) therein. RESULTS: Five commercially available propenylbenzene-rich oils were screened, of which betel (Piper betle L.) oil was identified as a potent natural phytotoxin. It dose-dependently inhibited wheatgrass (Triticum aestivum) seed germination and growth in water and agar medium with half maximal inhibitory concentration (IC50 ) in the range 23.2-122.7 µg mL-1 . Phytotoxicity-guided fractionation and purification revealed chavibetol as the major and most potent phytotoxic constituent of betel oil, followed by chavibetol acetate. A structure-activity relationship study involving 12 propenylbenzenes indicated the structural and positional importance of aromatic substitutions for the activity. Furthermore, the phytotoxic efficacy of chavibetol was established against wheatgrass germination and growth in water (IC50 15.8-53.4 µg mL-1 ), agar (IC50 34.4-53.6 µg mL-1 ) and aerial (IC50 1.7-4.5 mg L-1 ) media with a more pronounced effect on the radicle. Also, in open phytojars, chavibetol efficiently inhibited the growth of 3-7-day-old bermudagrass (Cynodon dactylon) seedlings when sprayed directly (IC50 2.3-3.4 mg jar-1 ) or supplemented in agar (IC50 116.6-139.1 µg mL-1 ). The growth of pre-germinated green amaranth (Amaranthus viridis) was inhibited more effectively in both application modes (1.2-1.4 mg jar-1 and IC50 26.8-31.4 µg mL-1 respectively). CONCLUSION: The study concluded betel oil as a potent phytotoxic herbal extract and its major constituent chavibetol as a promising volatile phytotoxin for the future management of weeds in their early phase of emergence. © 2023 Society of Chemical Industry.

Mushroom-Mediated Reductive Bioconversion of Aldehyde-Rich Essential Oils for Aroma Alteration: A Rose-like Floral Bioflavor from Citronella Oil.

The bioflavors are of high demand in food and beverage industries. The current study identified reductive processes mediated by mushroom species to alter the aroma of aldehyde-rich essential oils in the submerged culture. Neofomitella polyzonata, a polypore mushroom, reduced citronellal and citral in the citronella oil into corresponding alcohols that altered the oil aroma, creating a new bioflavor. The screening with 43 aldehydes showed its broad substrate scope within aromatic and linear aldehydes, yet influenced by the electronic and steric factors. Under an optimized condition, it efficiently converted up to 1.5 g/L citrusy and sharp citronella oil into a terpene alcohol-rich (citronellol and geraniol) floral, sweet, fresh, and rosy oily product within 12 h. The preparative-scale fermentation in the shake flask followed by distillation, an organic solvent-free downstream process, furnished the product in 87.2% w/w yield. Detailed sensory analyses and volatile chemo-profiling established the uniqueness in the product aroma and identified citronellol and geraniol as the key odorants. The chemometric analysis found best compositional similarity of this product with Damask or Turkish rose oils. The preference test for the water flavored with the fermented product (0.001-0.005% v/v) indicated its potential as a rosy bioflavor for the beverages.

A high performance thin layer chromatography (HPTLC) method for the quality assessment of agarwood (Aquilaria malaccensis) oil from Northeast India.

The high-value agarwood oil, largely used in perfumery is generally graded by the traditional method of sensorial assessment. The compositional complexity and variation made its quality control challenging. Besides, non-volatile contaminants and adulterants are the bottlenecks in gas-chromatographic detection. Herein, a HPTLC based technique was developed for the quality assessment of agarwood oil from Northeast India. A 'marker band' (anisylacetone and oxygenated sesquiterpene rich) on HPTLC profile, containing major peaks of the oil and characteristic agarwood aroma was quantified to assess the quality. The developed method was validated in terms of specificity, linearity, sensitivity, recovery and precision. The application of the method in test samples of three different grades indicated a positive correlation between 'marker band' quantity and oil quality. Its abundance in the superior grade oil was >50% and <20% in poor grade. It can be an efficient analytical tool for the quality assessment and grading of agarwood oil.

Thermolabile essential oils, aromas and flavours: Degradation pathways, effect of thermal processing and alteration of sensory quality.

Plant-based aroma chemicals, constituting the essential oils play a great role as the natural flavours and preservatives in the food industries. Many of these metabolites are susceptible to degradation under heat (i.e. thermolabile aroma chemicals) which may influence the organoleptic properties of the end-products e.g. essential oil, oleoresin, dry herb, tea and packaged juice. The current review identified in total 42 thermolabile aroma and/or flavour molecules belonging to monoterpenoids, sesquiterpenoids and phenolics. The probable pathway of their degradation and its promoting conditions were also described. Degradation pathways were categorized into five major classes including oxidation, C-C bond cleavage, elimination, hydrolysis and rearrangement. Numerous evidences were cited in support of the thermosensitivity of these phytochemicals under pyrolytic, thermal heating or gas chromatographic conditions. Various post-harvest processes involved in the manufacturing such as drying and distillation of the crops or thermal treatment of the food-products for storage were highlighted as the root cause of degradation. The influence of thermolabile aroma chemicals to maintain the sensory quality of the end-products such as citrus juices, floral oils and thermally cooked foods was discussed in detail. In the present article, detailed insight into the chemical and sensory aspects of thermosensitive aromas and flavours was provided, covering the period from 1990 up to 2020.

Nutmegs and wild nutmegs: An update on ethnomedicines, phytochemicals, pharmacology, and toxicity of the Myristicaceae species.

Prized medicinal spice true nutmeg is obtained from Myristica fragrans Houtt. Rest species of the family Myristicaceae are known as wild nutmegs. Nutmegs and wild nutmegs are a rich reservoir of bioactive molecules and used in traditional medicines of Europe, Asia, Africa, America against madness, convulsion, cancer, skin infection, malaria, diarrhea, rheumatism, asthma, cough, cold, as stimulant, tonics, and psychotomimetic agents. Nutmegs are cultivated around the tropics for high-value commercial spice, used in global cuisine. A thorough literature survey of peer-reviewed publications, scientific online databases, authentic webpages, and regulatory guidelines found major phytochemicals namely, terpenes, fatty acids, phenylpropanoids, alkanes, lignans, flavonoids, coumarins, and indole alkaloids. Scientific names, synonyms were verified with www.theplantlist.org. Pharmacological evaluation of extracts and isolated biomarkers showed cholinesterase inhibitory, anxiolytic, neuroprotective, anti-inflammatory, immunomodulatory, antinociceptive, anticancer, antimicrobial, antiprotozoal, antidiabetic, antidiarrhoeal activities, and toxicity through in-vitro, in-vivo studies. Human clinical trials were very few. Most of the pharmacological studies were not conducted as per current guidelines of natural products to ensure repeatability, safety, and translational use in human therapeutics. Rigorous pharmacological evaluation and randomized double-blind clinical trials are recommended to analyze the efficacy and therapeutic potential of nutmeg and wild nutmegs in anxiety, Alzheimer's disease, autism, schizophrenia, stroke, cancer, and others.

Evaluation of Postharvest Drying, Key Odorants, and Phytotoxins in Plai (Zingiber montanum) Essential Oil.

Plai or cassumunar ginger (Zingiber montanum), mainly distributed in tropical Asia, is an essential oil-bearing rhizomatous crop belonging to the Zingiberaceae family. Rhizomes and essential oil of this herb are used in culinary as flavoring agents, traditional medicines, and aromatherapy. In this study, the effect of different postharvest drying methods (air-, oven-drying at 40 and 60 °C, sun-, microwave-, and freeze-drying) of its sliced rhizome on the essential oil yield, composition, and sensory quality was investigated. The major key odorants and phytotoxins in its essential oil were identified for the first time through sensory- or bioassay-guided fractionation. Although the drying methods did not alter the oil composition significantly, oven-drying at 40 °C and freeze-drying produced the highest oil yield (81.0% of fresh rhizome) while maintaining the sensory quality. 4-Terpineol was found to be the majorly abundant key odorant in its oil through detailed sensory analysis. This oxygenated monoterpene was also demonstrated to be the major phytotoxin negatively affecting seed germination and shoot and root growth of wheatgrass seeds with IC50 values of 0.67, 0.10, and 0.17 mM, respectively. The current study is beneficial for further value addition of this crop in food industries and the agricultural sector.

A sensitive 1 H NMR spectroscopic method for the quantification of capsaicin and capsaicinoid: morpho-chemical characterisation of chili land races from northeast India.

INTRODUCTION: Proton (1 H) nuclear magnetic resonance (NMR) spectroscopy based analytical method for the quantification of capsaicin (major pungent principle of chili) has certain advantages including short data acquisition time and better structural authentication. Earlier NMR methods are associated with either of the bottlenecks such as low or lack of information on the sensitivity and scope for the quantification of total capsaicinoid. OBJECTIVE: To develop a sensitive 1 H quantitative NMR (qNMR) technique for capsaicin and total capsaicinoid in dry chili and chili oleoresin and to demonstrate its applicability in a real sample set. METHOD: A 1 H qNMR method was developed using benzene as the internal standard for the quantification of capsaicin (terminal methyl signal) as well as total capsaicinoid (benzyl methylene signal) in dry chili and oleoresin and validated in terms of specificity, linearity, sensitivity, accuracy and precision. RESULTS: The developed 1 H qNMR method was specific, sensitive (limit of detection 4.4 µg/mL and limit of quantitation 14.8 µg/mL), linear in the range 0.083-8.33 mg/mL of capsaicin, accurate and precise. The credibility of the developed method was showcased in the morpho-chemical characterisation of commercially available 15 chili land races from northeast India. The analysis identified the land races with a wide range of capsaicin (trace to 1.49% in the dry fruit and trace to 6.21% in the oleoresin w/w) and oleoresin content (3.35-26.78% w/w). CONCLUSION: The standardized 1 H qNMR method facilitated the findings of chemical basis for the selection of chili land races from this region, capable of producing high-yielding oleoresin with intended degree of pungency.