Composition and antimicrobial activity of the essential oils from the Phebalium squamulosum species complex (Rutaceae) in New South Wales, Australia

Fundamental Chemistry of Essential Oils and Volatile Organic Compounds, Methods of Analysis and Authentication

The current text provides a comprehensive introduction to essential oils, their biosynthesis, naming, analysis, and chemistry. Importantly, this text quickly brings the reader up to a level of competence in the authentication of essential oils and their components. It gives detailed descriptions of enantiomers and other forms of stereoisomers relevant to the study of natural volatiles and essential oils. The text also describes GC-MS work and provides tips on rapid calculation of arithmetic indices, how to interpret suggested names from the NIST mass spectral library, and what additional efforts are required to validate essential oils and defeat sophisticated adulteration tactics. In brief, essential oils are mixtures of volatile organic compounds that were driven out of the raw plant material in distillation, condensed into an oil that is strongly aroma emitting, and collected in a vessel as the top layer (uncommonly bottom layer) of two phase separated liquids: oil and water. Essential oils commonly include components derived from two biosynthetic groups, being terpenes (monoterpenes, sesquiterpenes and their derivatives) and phenylpropanoids (aromatic ring with a propene tail). The current text provides details of how terpenes and phenylpropanoids are further categorised according to their parent skeleton, then recognised by the character of oxidation, which may be from oxygen, nitrogen, or sulphur, or the presence/absence of a double bond. The essential oil's science niche is an epicentre of individuals from diverse backgrounds, such as aromatherapy, pharmacy, synthetic and analytical chemistry, or the hobbyist. To make the science more accessible to the curious student or researcher, it was necessary to write this fundamentals-level introduction to the chemistry of essential oils (i.e., organic chemistry in the context of essential oils), which is herein presented as a comprehensive and accessible overview. Lastly, the current review constitutes the only resource that highlights common errors and explains in simplistic detail how to correctly interpret GC-MS data then accurately present the respective chemical information to the wider scientific audience. Therefore, detailed study of the contents herein will equip the individual with prerequisite knowledge necessary to effectively analyse an essential oil and make qualified judgement on its authenticity.

Antioxidant and Antibacterial Activity of Nepeta × faassenii Bergmans ex Stearn Essential Oil

This study was designed to evaluate, for the first time, the antioxidant and antimicrobial activities of Nepeta × faassenii essential oil (NEO). Twenty-six compounds were identified by gas chromatography and mass spectrometry analysis, of which 4a alpha,7alpha,7a alpha-nepetalactone (34.12%), elemol (23.23%), spiro(5,6)dodecane (13.73%), and 3,4 alpha-dihydro-4a alpha, 7 alpha, 7a alpha-nepetalactone (7.93%) were the major compounds. The NEO exhibited broad-spectrum antibacterial effects, and possesses potent antifungal activity on Candida albicans and Candida parapsilosis. NEO’s antioxidant activity was evaluated against cold-pressed sunflowers oil by peroxide, thiobarbituric acid, 1,1-diphenyl- 2-picrylhydrazyl radical, and β-carotene/linoleic acid bleaching methods. The NEO showed strong scavenging (IC50: 0.032 ± 0.005 mg/mL) and relative antioxidative activity (RAA%: 92.31 ± 0.17%) in 1,1-diphenyl- 2-picrylhydrazyl radical and β-carotene/linoleic acid bleaching assays, respectively. Moreover, during 24 days of the incubation period, the oil inhibits the primary lipid oxidation significantly better (p < 0.05) than butylated hydroxyanisole (BHA). In the case of secondary lipid oxidation, the oil performed significantly better (p < 0.001) than BHA from day 8 to day 12 of the incubation period. The biological activities recorded suggest that NEO may represent an antioxidant and antimicrobial agent with applications in medicine or the food industry.

From Petri Dish to Patient: Bioavailability Estimation and Mechanism of Action for Antimicrobial and Immunomodulatory Natural Products

The new era of multidrug resistance of pathogens against frontline antibiotics has compromised the immense therapeutic gains of the 'golden age,' stimulating a resurgence in antimicrobial research focused on antimicrobial and immunomodulatory components of botanical, fungal or microbial origin. While much valuable information has been amassed on the potency of crude extracts and, indeed, purified compounds there are too many reports that uncritically extrapolate observed in vitro activity to presumed ingestive and/or topical therapeutic value, particularly in the discipline of ethnopharmacology. Thus, natural product researchers would benefit from a basic pharmacokinetic and pharmacodynamic understanding. Furthermore, therapeutic success of complex mixtures or single components derived therefrom is not always proportionate to their MIC values, since immunomodulation can be the dominant mechanism of action. Researchers often fail to acknowledge this, particularly when 'null' activity is observed. In this review we introduce the most up to date theories of oral and topical bioavailability including the metabolic processes affecting xenobiotic biotransformation before and after drugs reach the site of their action in the body. We briefly examine the common methodologies employed in antimicrobial, immunomodulatory and pharmacokinetic research. Importantly, we emphasize the contribution of synergies and/or antagonisms in complex mixtures as they affect absorptive processes in the body and sometimes potentiate activity. Strictly in the context of natural product research, it is important to acknowledge the potential for chemotypic variation within important medicinal plants. Furthermore, polar head space and rotatable bonds give a priori indications of the likelihood of bioavailability of active metabolites. Considering this and other relatively simple chemical insights, we hope to provide the basis for a more rigorous scientific assessment, enabling researchers to predict the likelihood that observed in vitro anti-infective activity will translate to in vivo outcomes in a therapeutic context. We give worked examples of tentative pharmacokinetic assessment of some well-known medicinal plants.

Chemical Composition of the Essential Oil of Bupleurum Fontanesii (Apiaceae) Growing Wild in Sicily and its Activity on Microorganisms Affecting Historical Art Crafts

Hydrodistillation of the flowers (BpFl) of and fruits (BpFr) of Bupleurum fontanesii Guss. ex Caruel gave two oils that were analyzed by GC and GC-MS. The main components were α-elemol (16.7%), caryophyllene oxide (16.4%) and heptacosane (15.9%) in BpFl, and spathulenol (16.8%), caryophylladienol I (13.2%) and α-elemol (12.8%) in BpFr. A good antimicrobial activity against several microorganisms, including Bacillus subtilis, Staphylococcus aureus, Fusarium oxysporum and Aspergillus niger, all infesting historical art craft, was also determined.