Essential Oil Constituents as Anti-Inflammatory and Neuroprotective Agents: An Insight through Microglia Modulation.

Microglia are key players in the brain's innate immune response, contributing to homeostatic and reparative functions but also to inflammatory and underlying mechanisms of neurodegeneration. Targeting microglia and modulating their function may have therapeutic potential for mitigating neuroinflammation and neurodegeneration. The anti-inflammatory properties of essential oils suggest that some of their components may be useful in regulating microglial function and microglial-associated neuroinflammation. This study, starting from the ethnopharmacological premises of the therapeutic benefits of aromatic plants, assessed the evidence for the essential oil modulation of microglia, investigating their potential pharmacological mechanisms. Current knowledge of the phytoconstituents, safety of essential oil components, and anti-inflammatory and potential neuroprotective effects were reviewed. This review encompasses essential oils of Thymus spp., Artemisia spp., Ziziphora clinopodioides, Valeriana jatamansi, Acorus spp., and others as well as some of their components including 1,8-cineole, ß-caryophyllene, ß-patchoulene, carvacrol, ß-ionone, eugenol, geraniol, menthol, linalool, thymol, α-asarone, and α-thujone. Essential oils that target PPAR/PI3K-Akt/MAPK signalling pathways could supplement other approaches to modulate microglial-associated inflammation to treat neurodegenerative diseases, particularly in cases where reactive microglia play a part in the pathophysiological mechanisms underlying neurodegeneration.

Immunomodulatory activity of marine natural products: Synthesis, spectral characterization and toxicity assessment of natural and related synthetic iodinated tyramides.

The toxicity of natural marine iodoarenes or their synthetic counterparts is widely unknown despite the fact that triiodothyronine and thyroxine are members of this class. In this work we aimed to expand such knowledge on iodinated marine natural products and tested an ascidian (Didemnum rubeum) metabolite, N-(3,5-diiodo-4-methoxyphenethyl)benzamide, together with closely related synthetic iodinated tyramides: N-(2,5-diiodo-4-methoxyphenethyl)benzamide, N-(3-iodo-4-methoxyphenethyl)benzamide, N-(4-methoxyphenethyl)benzamide, and N-(3-iodo-4-methoxyphenethyl)formamide, for their effect on the viability of rat macrophages, as well as acute toxicity on Artemia salina. The tested tyramides exerted a varying degree of toxicity towards brine shrimps, but in certain cases, the determined lethal concentrations were even lower than those of known toxicants (e.g. strychnine sulfate, SDS). The toxicity was highly dependent on the structure of these mutually related compounds, while the natural one was shown to be the most toxic. In the case of macrophage cultures, the tested tyramides exerted much less toxicity but were found to have an effect on the functioning of these normal immune cells. The samples of the tyramides were obtained by synthesis, and were fully structurally and spectrally characterized, which also provided corroboration of the proposed structure of the natural product originally isolated in minute amounts.

Toxic essential oils: anxiolytic, antinociceptive and antimicrobial properties of the yarrow Achillea umbellata Sibth. et Sm. (Asteraceae) volatiles.

Many plant species are used for medicinal purposes without the knowledge of their possible toxic effect. The ethnopharmacologically renowned genus Achillea L. (Asteraceae) is even more troublesome in this respect since different taxa are believed to have the same beneficial properties as A. millefolium. According to the median lethal i.p. dose (LD(50)=853 mg/kg, mice), the volatiles of Achillea umbellata Sibth. et Sm. are more toxic than the thujone-containing essential oils (LD(50)>960 mg/kg). A GC-MS analysis of A. umbellata oil revealed the presence of a series of fragranyl esters (six new natural products). The major constituents of this oil, the rare monoterpene alcohol fragranol and fragranyl acetate, and one more ester (benzoate), as well as the oil itself, showed antianxiety, analgesic and, in some instances, paralyzing properties at 50-150 mg/kg but these are very likely sign of intoxication and not of possible beneficial effects of the plant volatiles. Testing of antimicrobial activity demonstrated that the oil possesses moderate activity against pathogenic microorganisms, but the effect of the oil differs in pro- and eukaryotic cells. According to the results obtained, fragranol may be considered as the main active principle responsible for the observed activity/toxicity.