The Volatile Phytochemistry of Seven Native American Aromatic Medicinal Plants

Phytochemistry and Biological Profile of Gaultheria procumbens L. and Wintergreen Essential Oil: From Traditional Application to Molecular Mechanisms and Therapeutic Targets

Gaultheria procumbens L. is a medicinal plant whose aerial parts (leaves, stems, and fruits) and methyl salicylate-rich essential oil (wintergreen oil) are used in phytotherapy to treat inflammation, muscular pain, and infection-related disorders. This overview summarises the current knowledge about ethnobotany, phytochemistry, pharmacology, molecular mechanisms, biocompatibility, and traditional use of G. procumbens and the wintergreen oil distilled from different plant organs. Over 70 hydrophilic compounds, including methyl salicylate glycosides, flavonoids, procyanidins, free catechins, caffeoylquinic acids, and simple phenolic acids, have been identified in G. procumbens plant parts. Moreover, aliphatic compounds, triterpene acids, and sterols have been revealed in lipophilic fractions. Furthermore, over 130 volatile compounds have been detected in wintergreen oil with dominating methyl salicylate (96.9-100%). The accumulated research indicates that mainly hydrophilic non-volatiles are responsible for the pharmacological effects of G. procumbens, primarily its potent anti-inflammatory, antioxidant, and photoprotective activity, with mechanisms verified in vitro and ex vivo in cellular and cell-free assays. The biological effectiveness of the dominant methyl salicylate glycoside-gaultherin-has also been confirmed in animals. Wintergreen oil is reported as a potent anti-inflammatory agent exhibiting moderate antioxidant and antimicrobial activity in vitro and significant insecticidal and larvicidal capacity. Together, G. procumbens accumulate a diverse fraction of polyphenols, triterpenes, and volatiles with validated in vitro and ex vivo biological activity but with the absence of in vivo studies, especially clinical trials concerning effective dose determination and toxicological verification and technological research, including drug formulation.

Agastache Species: A Comprehensive Review on Phytochemical Composition and Therapeutic Properties

The Agastache genus is part of the Lamiaceae family and is native to North America, while one species, Agastache rugosa (A. rugosa), is native to East Asia. A review on the phytochemistry and bioactivity of Agastache genus was last performed in 2014. Since then, a lot of progress has been made on the characterization of the phytochemical and pharmacological profiles of Agastache species. Thus, the purpose of this paper is to present a summary of the findings on the phytochemistry and biological effects of several Agastache species, including both extracts and essential oil characterization. We performed a comprehensive search using PubMed and Scopus databases, following PRISMA criteria regarding the study selection process. The available data is focused mainly on the description of the chemical composition and bioactivity of A. rugosa, with fewer reports referring to Agastache mexicana (A. mexicana) and Agastache foeniculum (A. foeniculum). Agastache species are characterized by the dominance of flavonoids and phenolic acids, as well as volatile compounds, particularly phenylpropanoids and monoterpenes. Moreover, a series of pharmacological effects, including antioxidant, cytotoxic, antimicrobial, anti-atherosclerotic, and cardioprotective properties, have been reported for species from the Agastache genus.

Bridging the Chemical Profile and Biological Activities of a New Variety of Agastache foeniculum (Pursh) Kuntze Extracts and Essential Oil

This study investigated the phytochemical content of alcoholic extracts and essential oil of a new variety of medicinal plants, Agastache foeniculum (Pursh), which Kuntze adapted for cultivation in Romania, namely “Aromat de Buzău”. The essential oil was investigated by GC-MS, while the identification and quantification of various compounds from alcoholic extracts were performed by HPLC-DAD. The total phenol and flavonoid contents of the extracts were evaluated by using standard phytochemical methods. The antioxidant activities of ethanol, methanol extracts, and essential oil of the plant were also assessed against 2,2′-diphenyl-1-picrylhydrazyl (DPPH•), 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS•+), and by ferric reducing power (FRAP) using spectroscopic methods. Cyclic voltammetry was used to evaluate the antioxidant capacity of the essential oil. The concentrations of phenolic compounds were higher in methanolic extract compared to ethanolic extract. A significant correlation was found between total phenol and total flavonoid contents (r = 0.9087). Significant high correlations were also found between the total phenolic compounds and the antioxidant activities of the extracts (r ≥ 0.8600, p < 0.05). In addition, the extracts and essential oil showed good antioxidant and xanthine oxidase inhibitory activities. Estragole was detected as the major constituent of the essential oil (94.89%). The cytotoxic activity of the essential oil was evaluated by the MTT assay. At lower concentrations (1 µg/mL) high cytotoxicity against MCF-7 breast cancer cells was observed but not on the non-tumoral dermal fibroblasts (HDF) which indicated selectivity for cancer cells and suggests the presence of biologically active components that contribute to the observed high cytotoxic effect. Findings from the present study offer new perspectives on the use of A. foeniculum as a potential source of bioactive compounds and a good candidate for pharmaceutical plant-based products.

Characterization of Odorants in Loomis' Mountain Mint, Pycnanthemum loomisii

Loomis' mountain mint, Pycnanthemum loomisii Nuttall, is a species of mint native to the American Southeast. In the present study, 38 odorants were identified employing aroma extract dilution analysis (AEDA) performed on a distillate prepared by solvent extraction and solvent-assisted flavor evaporation (SAFE) distillation of dried P. loomisii. Seven odorants with flavor dilution (FD) factors ≥16 were quantitated using stable isotope dilution assays (SIDA), and their odor activity values (OAV) were calculated. In addition, the stereochemical composition of chiral odorants was also determined by chiral chromatography. Odor simulation experiments demonstrated that when 1,8-cineole (eucalyptus; OAV 6400), linalool (floral, citrus; OAV 120), β-ionone (floral, violet; OAV 86), borneol (earthy; OAV 56), and eugenol (clove; OAV 2.5) were combined in their natural concentrations, the model successfully mimicked the plant's aroma. The results of this investigation provide a foundation for additional investigations into the natural variation in aroma chemistry of different selections of P. loomisii and other members of the Pycnanthemum genus.

Characterization of Odorants in White Leaf Mountain Mint, Pycnanthemum albescens

White leaf mountain mint, Pycnanthemum albescens Torrey & A. Gray, also known as white mountain mint or white leaved mountain mint, is a species endemic in the American Southeast. In the present study, 24 odorants were identified using solvent-assisted flavor evaporation, aroma extract dilution analysis, and gas chromatography-mass spectrometry. Nine odorants with flavor dilution factors ≥16 were quantitated by stable isotope dilution assays, and odor activity values (OAVs) were calculated. In addition, the enantiomeric proportions of several chiral odorants were determined by chiral chromatography. Odorants with OAV ≥1 included 1,8-cineole (eucalyptus; OAV 9200), myrcene (terpeny; OAV 1400), linalool (floral, citrus; OAV 370), β-ionone (floral, violet; OAV 64), borneol (earthy; OAV 55), bornyl acetate (earthy, fruity; OAV 19), and eugenol (clove; OAV 3.1). Odor simulation experiments revealed that a mixture of the odorants with OAV ≥1 successfully mimicked the odor of an aqueous extract of the plant when combined in their natural concentrations. This study lays the groundwork for future studies aimed at determining the natural aroma variation within different populations of P. albescens and aids in the future development of selections and hybrids with targeted aroma profiles of commercial interest.

Characterization of Odorants in Southern Mountain Mint, Pycnanthemum pycnanthemoides

Southern mountain mint, Pycnanthemum pycnanthemoides (Leavenw.) Fernald, is a mountain mint species endemic to the southeastern United States. The odorants responsible for the plant's odor have not been previously characterized. In this study, 28 odorants were identified in a high-vacuum distillate of P. pycnanthemoides employing gas chromatography-olfactometry and gas chromatography-mass spectrometry. Flavor dilution (FD) factors were determined by aroma extract dilution analysis. Ten odorants with FD factors ≥16 were quantitated by stable isotope dilution assays, odor activity values (OAVs) were calculated, and the stereochemistry of chiral odorants was determined. Odorants with OAV ≥1 included β-ionone (floral, violet; OAV 310), piperitenone (mint; OAV 100), piperitone (mint; OAV 87), linalool (floral, citrus; OAV 45), myrcene (terpeny; OAV 35), (R)-(+)-pulegone (mint, medicinal; OAV 18), (2S,5R)-(-)-menthone (mint, fresh; OAV 6.6), and 1,8-cineole (eucalyptus; OAV 4.0). An odor simulation model based on the quantitative analysis was a close match to the sensory attributes of an aqueous infusion of dried P. pycnanthemoides. The study's results establish insights into the complex odor profile of P. pycnanthemoides and provide a foundation for future studies on the odor variability within P. pycnanthemoides and other species of the Pycnanthemum genus.

Nephroprotective Plants: A Review on the Use in Pre-Renal and Post-Renal Diseases

Kidney diseases are expected to become the fifth leading cause of death by 2040. Several physiological failures classified as pre-, intra-, and post-renal factors induce kidney damage. Diabetes, liver pathologies, rhabdomyolysis, and intestinal microbiota have been identified as pre-renal factors, and lithiasis or blood clots in the ureters, prostate cancer, urethral obstructions, prostate elongation, and urinary tract infections are post-renal factors. Additionally, the nephrotoxicity of drugs has been highlighted as a crucial factor inducing kidney injuries. Due to the adverse effects of drugs, it is necessary to point to other alternatives to complement the treatment of these diseases, such as nephroprotective agents. Plants are a wide source of nephroprotective substances and can have beneficial effects in different levels of the physiological pathways which lead to kidney damage. In traditional medicines, plants are used as antioxidants, anti-inflammatories, diuretics, and anticancer agents, among other benefits. However, the mechanism of action of some plants empirically used remains unknown and scientific data are required to support their nephroprotective effects. The present work reviewed the plants with a beneficial effect on kidney diseases. The classification of nephroprotective plants according to the clinical definition of pre-renal, intrinsic, and post-renal factors is proposed to orient their use as complementary treatments.

Gamma radiation crosslinking of PVA/myrrh resin thin film for improving the post-harvest time of lemon fruits

Preparation of a thin film of polyvinyl alcohol (PVA)/myrrh natural resin using a low gamma irradiation dose (1 kGy) was investigated towards increasing the post-harvest time of lemon fruit. Different analytical techniques, such as Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and mapping techniques were used to characterize the prepared thin film. This investigation was carried out to evaluate the effect of different concentrations of myrrh as an edible coating in prolonging shelf life and preserving the quality of lemon fruits (Citrus aurantifolia). Lemons were immersed directly in PVA solution containing 1%, 2%, and 3% concentrations of myrrh and then stored at ambient (25 ± 1 °C) and low (4 ± 1 °C) temperatures. The disease severity, acidity, total soluble solids (TSS), and ascorbic acid contents were tested after the coating with the PVA/myrrh thin film at different temperatures (4 °C and 25 °C) for different storage times (7 and 14 days). The application of different concentrations of the synthesized PVA/myrrh thin film (1%, 2%, and 3%) significantly reduced green mold disease symptoms and disease severity in the lemon fruits. The acidity value (pH value) was the lowest for the 2% myrrh treatment after 7 °C days at 25 °C, followed by the 1% myrrh treatment under the same conditions. The highest TSS was observed after the treatment for 7 days at 25 °C, with a value of 8.1 g dL-1. A high ascorbic acid concentration (33.5 mg dL-1) was noted after coating the lemons with the 1% PVA/myrrh thin film for 7 days at 25 °C. The results show that the application of a PVA/myrrh thin film extends the shelf-life and maintains the quality of lemon fruits by decreasing the levels of evaporation from the fruits and loss of weight due to the delay of the complete ripening stage of the lemon fruits.

Green Leaf Volatile-Burst in Selaginella moellendorffii

Green leaf volatiles (GLVs) consist of six-carbon volatile aldehydes, alcohols, and their esters. They are formed from polyunsaturated fatty acids and are involved in the defense of plants against herbivores and pathogens. GLVs generally have low concentrations in intact healthy plant tissues, but the biosynthetic pathway to form GLVs is quickly activated by mechanical damage to tissues, an event called the GLV-burst. Most seed plants have the ability to implement GLV-burst; however, this potential in non-seed plants has not been extensively researched. In this study, we examined the GLV-burst capacity of monilophytes, lycophytes, and bryophytes, and confirmed that monilophytes and lycophytes showed substantial GLV-burst ability, while bryophytes did not, with a few exceptions. When the genome sequence of a model lycophyte, Selaginella moellendorffii was reviewed, 10 genes were found that showed high similarity with the non-canonical cytochrome P450 enzymes, CYP74s, specialized in oxylipin formation. Recombinant proteins expressed with Escherichia coli showed that one of them had the ability to encode allene oxide synthase, and another encoded hydroperoxide lyase (HPL), preferring linolenic acid 13-hydroperoxide, and it was inferred that this gene was responsible for GLV-burst in S. moellendorffii. Based on the phylogenetic tree constructed with CYP74s of non-seed and seed plants, we hypothesized that HPL was acquired independently in the lycophyte and seed plants through diversification of CYP74 genes.

Essential Oils of Four Virginia Mountain Mint (Pycnanthemum virginianum) Varieties Grown in North Alabama

Virginia mountain mint (Pycnanthemum virginianum) is a peppermint-flavored aromatic herb of the Lamiaceae and is mainly used for culinary, medicinal, aromatic, and ornamental purposes. North Alabama's climate is conducive to growing mint for essential oils used in culinary, confectionery, and medicinal purposes. There is, however, a need for varieties of P. virginianum that can be adapted and easily grown for production in North Alabama. Towards this end, four field-grown varieties with three harvesting times (M1H1, M1H2, M1H3; M2H1, M2H2, M2H3; M3H1, M3H2, M3H3, M4H1, M4H2, M4H3) were evaluated for relative differences in essential oil yield and composition. Thirty-day-old greenhouse-grown plants of the four varieties were transplanted on raised beds in the field at the Alabama A & M University Research Station in North Alabama. The plots were arranged in a randomized complete block with three replications. The study's objective was to compare the four varieties for essential oil yield and their composition at three harvest times, 135, 155, and 170 days after planting (DAP). Essential oils were obtained by hydrodistillation with continuous extraction with dichloromethane using a Likens-Nickerson apparatus and analyzed by gas chromatographic techniques. At the first harvest, the essential oil yield of the four varieties showed that M1H1 had a yield of 1.15%, higher than M2H1, M3H1, and M4H1 with 0.91, 0.76, and 1.03%, respectively. The isomenthone concentrations increased dramatically through the season in M1 (M1H1, M1H2, M1H3) by 19.93, 54.7, and 69.31%, and M3 (M3H1, M3H2, M3H3) by 1.81, 48.02, and 65.83%, respectively. However, it increased only slightly in M2 and M4. The thymol concentration decreased slightly but not significantly in all four varieties; the thymol in M2 and M4 was very high compared with M1 and M3. The study showed that mountain mint offers potential for production in North Alabama. Two varieties, M1 and M3, merit further studies to determine yield stability, essential oil yield, composition, and cultivation development practices.