As the largest class of natural products, terpenes have a variety of roles in mediating antagonistic and beneficial interactions among organisms. They defend many species of plants, animals and microorganisms against predators, pathogens and competitors, and they are involved in conveying messages to conspecifics and mutualists regarding the presence of food, mates and enemies. Despite the diversity of terpenes known, it is striking how phylogenetically distant organisms have come to use similar structures for common purposes. New natural roles undoubtedly remain to be discovered for this large class of compounds, given that such a small percentage of terpenes has been investigated so far.

The function of terpene natural products in the natural world.

https://www.srs.fs.usda.gov/pubs/ja/ja_lee001.pdf

Fumigation toxicity of monoterpenoids to several stored product insects

The therapeutic value of synergistic interactions has been known since antiquity, and many different cultural healing systems still rely on this principle in the belief that combination therapy may enhance efficacy. This paper intends to provide an overview, from an antimicrobial perspective, on the research undertaken and interactive principles involved in pharmacognosy studies. Methods used to determine antimicrobial interactions include basic combination studies, the sum of the fractional inhibitory concentration index (ΣFIC), isobole interpretations, and death kinetic (time-kill) assays. The various interactions are discussed with reference to molecules, different plant parts or fractions, different plant species, and combinations with nonbotanical antimicrobial agents. It is recommended for future development in the field of phytosynergy that consideration should be given to the selection criteria for the two inhibitors. A more conservative approach should be adopted when classifying synergy. When examining interactions in plant-based studies, antagonistic interactions should not be ignored. Combinations involving more than two test samples should be examined where applicable, and very importantly, the mechanism of action of synergistic interactions should be given precedence. It is encouraging to observe the upsurge in papers exploring the complex interactions of medicinal plants, and undoubtedly this will become increasingly important in our continued quest to understand the mechanism of action of phytotherapy. The scientific validation of efficacious antimicrobial combinations could lead to patentable entities making research in the field of phytosynergy not only academically rewarding but also commercially relevant.

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Plant-Based Antimicrobial Studies – Methods and Approaches to Study the Interaction between Natural Products

Phytochemical screening, total phenolics and antioxidant activities of bark and leaf extracts of Goniothalamus velutinus (Airy Shaw) from Brunei Darussalam

The antimicrobial activity of the essential oils of Mentha spicata L. and Anethum sowa Roxb. (Indian dill) were studied. The major chemical constituents of the hydrodistilled essential oils and their major isolates from cultivated M. spicata and A. sowa were identified by IR, 1H- and 13C-NMR and GC: (S)-(−)-limonene (27.3%) and (S)-(−)-carvone (56.6%) (representing 83.9% of the spearmint oil) and (R)-(+)-limonene (21.4%), dihydrocarvone (5.0%), (R)-(+)-carvone (50.4%) and dillapiole (17.7%) (together 76.9% in Indian dill oil), respectively. In vitro bioactivity evaluation of the isolated oil components revealed that both the optical isomers of carvone were active against a wide spectrum of human pathogenic fungi and bacteria tested. (R)-(+)-limonene showed comparable bioactivity profile over the (S)-(−)-isomer. The activity of these monoterpene enantiomers was found to be comparable to the bioactivity of the oils in which they occurred. Copyright © 2001 John Wiley & Sons, Ltd.

Antimicrobial activity profiles of the two enantiomers of limonene and carvone isolated from the oils of Mentha spicata and Anethum sowa

The steam distillate of the green leaves of Perilla frutescens has broad antimicrobial activity assumed from its use as food and food additives. The steam distillate mainly consists of perillaldehyde, limonene, β-caryophyllene, α-bergamotene, and linalool. The most abundant, perillaldehyde, inhibits moderately a broad range of both bacteria and fungi. Perillaldehyde work in synergy with polygodial not only against fungi but also against both Gram-positive and Gram-negative bacteria. Synergistic effects are evaluated by the fractional inhibition concentration method

Antimicrobial activity of the volatile constituents of Perilla frutescens and its synergistic effects with polygodial

Phenanthrene lactams from Goniothalamus velutinus

ABSTRAC~.-A novel hydrolyzable tannin, chinquapinic acid [3], was isolated from the MeOH extract of the epidermal powder found on the leaf underside of CbrysokpiS ~anpervimU inaddition totwoknown tannins,vescalagin11]andcastalagin(2]. Thestrucnveofchinquapinic acid was established through spectroscopic data and auto-conversion to vescalagin. Scanning electron microscopy showed the yellowish powder to be crystal-like in appearance. These tannins are first examples for this class of compounds found as exudates on a plant surface. Chrysolepis sempervirens (Kellogg) Hjelmq. formerly Castenopsis sempewirens (Fagaceae), commonly referred to as bush chinquapin, is an evergreen shrub growing on rocky slopes of the Sierra Neveda and in central Oregon. We found the leaf underside of Chr. sempewirens densely covered with agold-colored powder that was easily scraped off. This material was previously believed to be composed of feltlike hairs (1). However, scanning electron microscopy showed the leaves to be covered with crystal-like powders which dissolved in MeOH. This indicated that the powder consists of organic chemicals. Our interest was to discover what chemicals are exuded and what role they play in plants. Many studies have been reported that plants secrete chemicals such as sugars, enzymes, and waxes, and that chemicals exuded onto the plant surface may act as defense substances against attack from insects (2) or microorganisms (3). We now report the isolation, structure determination, and biological activity of a novel hydrolyzable tannin and two known related tannins from Chr. sempvirens.

A novel hydrolyzable tannin and related compounds isolated from the leaf surface of chrysolepis sempervirens

Scanning electron microscopy showed that the undersides of the leaves of Chrysolepis sempervirens (Fagaceae) are covered with crystalline epidermal powder. An examination of the chemical composition of the epidermal powder has led to the isolation and characterization of a new C-glycosidic, hydrolyzable tannin, chinquapinic acid (3), in addition to two known tannins, vescalagin (1) and castalagin (2). The structure and stereochemical properties of (3) were established by relying on analogies to castalagin and vescalagin, along with evidence gained from NMR experiments and conversion to vescalagin. These tannins have cytotoxic activities and are the first examples of this class of compound to be exuded from the plant surface.

Hasan Jaber

Papers

Antimicrobial activity of the volatile constituents of Perilla frutescens and its synergistic effects with polygodial

Phenanthrene lactams from Goniothalamus velutinus

A novel hydrolyzable tannin and related compounds isolated from the leaf surface of chrysolepis sempervirens

Chinquapinic Acid: A Novel Hydrolyzable Tannin Isolated from Chrysolepis Sempervirens