Phytochemical Investigation of Male and Female Hedyosmum scabrum (Ruiz & Pav.) Solms Leaves from Ecuador

Chemical and Biological Activity Profiling of Hedyosmum strigosum Todzia Essential Oil, an Aromatic Native Shrub from Southern Ecuador

The present study aimed to determine the chemical composition, enantiomeric distribution and the biological profile of Hedyosmum strigosum essential oil (EO). The antioxidant properties and anticholinesterase effect were measured by spectroscopic methods and antimicrobial potency assessed against 8 bacteria and two fungi. H. strigosum is a native shrub, particularly found in Ecuador and Colombia at 2000 to 3500 m a.s.l. Chemical composition was determined by GC-MS and GC-FID. A total of 44 compounds were detected, representing more than 92% of the EO composition. The main compounds were thymol (24.35, 22.48%), α-phellandrene (12.15, 13.93%), thymol acetate (6.59, 9.39%) and linalool (8.73, 5.82%), accounting for more than 51% of the EO. The enantioselective analysis revealed the presence of 5 pure enantiomers and 3 more as a racemic mixture. The EO exerted a strong antioxidant capacity, determined by ABTS assay, with a SC50 of 25.53 µg/mL and a strong and specific antimicrobial effect against Campylobacter jejuni with a MIC value of 125 µg/mL. A moderate acetylcholinesterase inhibitory effect was also observed with an IC50 value of 137.6 µg/mL. To the best of our knowledge this is the first report of the chemical composition and biological profile of H. strigosum EO.

Pharmacology and Phytochemistry of Ecuadorian Medicinal Plants: An Update and Perspectives

The use of plants as therapeutic agents is part of the traditional medicine that is practiced by many indigenous communities in Ecuador. The aim of this study was to update a review published in 2016 by including the studies that were carried out in the period 2016–July 2021 on about 120 Ecuadorian medicinal plants. Relevant data on raw extracts and isolated secondary metabolites were retrieved from different databases, resulting in 104 references. They included phytochemical and pharmacological studies on several non-volatile compounds, as well as the chemical composition of essential oils (EOs). The tested biological activities are also reported. The potential of Ecuadorian plants as sources of products for practical applications in different fields, as well the perspectives of future investigations, are discussed in the last part of the review.

Chemical and Enantioselective Analysis of the Essential Oils from Different Morphological Structures of Ocotea quixos (Lam.) Kosterm

The traditional Ecuadorian spice Ishpingo, characterized by a strong cinnamon-like aroma, is constituted by the dry cupules of Amazonian species Ocotea quixos. Nevertheless, bark and leaves also present aromatic properties and are sometimes used as substitutes. In the present study, the essential oils, distilled from these morphological structures, are comparatively analyzed for their chemical and enantiomeric compositions. A total of 88 components were identified with 2 orthogonal GC columns, whereas 79, corresponding to more than 94%, were also quantified with at least 1 column. Major compounds were (E)-methyl cinnamate in cupules (35.9-34.2%), (E)-cinnamaldehyde in bark (44.7-47.0%), and (E)-cinnamyl acetate (46.0-50.4%) in leaves. For what concerns the enantioselective analysis, 10 chiral terpenes and terpenoids were detected, of which 6 were present as enantiomeric pairs in at least 1 essential oil, the others being enantiomerically pure. Both quantitative and enantioselective analyses were submitted to Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA), where their results confirmed significative difference among the three products.

Variability of the Chemical Composition and Bioactivity between the Essential Oils Isolated from Male and Female Specimens of Hedyosmum racemosum (Ruiz & Pav.) G. Don

Hedyosmum racemosum (Ruiz & Pav.) G. is a native species of Ecuador used in traditional medicine for treatment of rheumatism, bronchitis, cold, cough, asthma, bone pain, and stomach pain. In this study, fresh H. racemosum leaves of male and female specimens were collected and subjected to hydrodistillation for the extraction of the essential oil. The chemical composition of male and female essential oil was determined by gas chromatography–gas chromatography equipped with a flame ionization detector and coupled to a mass spectrometer using a non-polar and a polar chromatographic column. The antibacterial activity was assayed against five Gram-positive and two Gram-negative bacteria, and two dermatophytes fungi. The scavenging radical properties of the essential oil were evaluated by DPPH and ABTS assays. The chemical analysis allowed us to identify forty-three compounds that represent more than 98% of the total composition. In the non-polar and polar column, α-phellandrene was the principal constituent in male (28.24 and 25.90%) and female (26.47 and 23.90%) essential oil. Other main compounds were methyl chavicol, germacrene D, methyl eugenol, and α-pinene. Female essential oil presented a strong activity against Klebsiella pneumoniae (ATCC 9997) with an minimum inhibitory concentration (MIC) of 500 μg/mL and a scavenging capacity SC₅₀ of 800 µg/mL.

Essential Oil and Major Non-Volatile Secondary Metabolites from the Leaves of Amazonian Piper subscutatum

The essential oil and the major non-volatile secondary metabolites from the leaves of Piper subscutatum (Miq.) C. DC. (Family Piperaceae), collected in the Ecuadorian Amazon, were analyzed for the first time in the present study. The essential oil was submitted to chemical and enantioselective analyses by GC-MS and GC-FID. (E)-β-caryophyllene (25.3-25.2%), β-chamigrene (10.3-7.8%), (E)-nerolidol (8.1-7.7%), β-selinene (7.2-7.7%), δ-cadinene (2.7-3.9%), bicyclogermacrene (3.7-2.4%), and β-pinene (2.6-3.4%) were the major components. The enantioselective analysis, carried out on a β-cyclodextrin-based column, showed four scalemic mixtures in which (1R,5R)-(+)-α-pinene, (1S,5S)-(-)-β-pinene, (S)-(-)-limonene, and (1R,2S,6S,7S,8S)-(-)-α-copaene were the major enantiomers, with enantiomeric excesses of 28.8%, 77.8%, 18.4%, and 6.0%, respectively. The study was complemented with the chemical analysis of the organic fraction dissolved in the hydrolate, whose major components were 6-methyl-5-hepten-2-one (63.7-64.4%) and linalool (6.5-6.0%). Concerning the non-volatile fraction, five lignans were the major components. (-)-Beilshminol B, (-)-grandisin, (-)-3',4'-methylenedioxy-3,4,5-trimethoxy-7,7'-epoxylignan, (-)-3',4'-methylenedioxy-3,4,5,5'-tetramethoxy-7,7'-epoxylignan, and (-)-3,4,3',4'-dimethylenedioxy-5,5'-dimethoxy-7,7'-epoxylignan were identified by means of NMR spectroscopy, mass spectrometry and X-ray crystallography. The absolute configuration 7S,8S,7'S,8'S was tentatively assigned to all of them.

A Novel Chemical Profile of a Selective In Vitro Cholinergic Essential Oil from Clinopodium taxifolium (Kunth) Govaerts (Lamiaceae), a Native Andean Species of Ecuador

A novel chemical profile essential oil, distilled from the aerial parts of Clinopodium taxifolium (Kunth) Govaerts (Lamiaceae), was analysed by Gas Chromatography-Mass Spectrometry (GC-MS, qualitative analysis) and Gas Chromatography with Flame Ionization Detector (GC-FID, quantitative analysis), with both polar and non-polar stationary phase columns. The chemical composition mostly consisted of sesquiterpenes and sesquiterpenoids (>70%), the main ones being (E)-β-caryophyllene (17.8%), α-copaene (10.5%), β-bourbonene (9.9%), δ-cadinene (6.6%), cis-cadina-1(6),4-diene (6.4%) and germacrene D (4.9%), with the non-polar column. The essential oil was then submitted to enantioselective GC analysis, with a diethyl-tert-butyldimethylsilyl-β-cyclodextrin diluted in PS-086 chiral selector, resulting in the following enantiomeric excesses for the chiral components: (1R,5S)-(-)-α-thujene (67.8%), (1R,5R)-(+)-α-pinene (85.5%), (1S,5S)-(-)-β-pinene (90.0%), (1S,5S)-(-)-sabinene (12.3%), (S)-(-)-limonene (88.1%), (S)-(+)-linalool (32.7%), (R)-(-)-terpinen-4-ol (9.3%), (S)-(-)-α-terpineol (71.2%) and (S)-(-)-germacrene D (89.0%). The inhibition activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) of C. taxifolium essential oil was then tested, resulting in selective activity against BChE with an IC50 value of 31.3 ± 3.0 μg/mL (positive control: donepezil, IC50 = 3.6 μg/mL).

The Flower Essential Oil of Dalea mutisii Kunth (Fabaceae) from Ecuador: Chemical, Enantioselective, and Olfactometric Analyses

An essential oil was distilled with 0.25% yield from fresh flowers of Dalea mutisii Kunth, a native species mainly growing in the Andean region of Ecuador. A total of 50 compounds were identified, and most of them were quantified. The chemical composition was characterized by the prevalence of monoterpene hydrocarbons (>90%). Major components were α-pinene (42.9%), β-pinene (15.1%), β-phellandrene (12.6%), myrcene (6.7%), and (Z)-β-ocimene (5.4%). The essential oil was then submitted to enantioselective analysis, with a 2,3-diethyl-6-tert-butyldimethylsilyl-β-cyclodextrin-based capillary column. An enantiomeric excess was measured for (1R,5R)-(+)-α-pinene (91.6%), (1R,5R)-(+)-β-pinene (15.2%), (R)-(-)-α-phellandrene (4.8%), and (R)-(-)-β-phellandrene (88.8%), whereas (R)-(+)-limonene was enantiomerically pure. A gas chromatography-olfactometry (GC-O) analysis was additionally carried out on this pleasantly fragrant essential oil, following an aroma extract dilution analysis (AEDA) approach. Main odorants were α-pinene, β-pinene, α-phellandrene, and (Z)-β-ocimene, with dilution factors (FD) of 8, 4, 2, and 2, respectively.

Chemical and Enantioselective Analysis of the Leaf Essential Oil from Piper coruscans Kunth (Piperaceae), a Costal and Amazonian Native Species of Ecuador

In the present study, an essential oil was distilled from the leaves of Piper coruscans Kunth, a native Amazonian species belonging to the family Piperaceae and quite common in Ecuador. The chemical analysis was performed by GC-MS (qualitative) and GC-FID (quantitative), on polar and non-polar columns, detecting a total of 58 compounds of which 52 were identified. All the identified compounds were quantified. The essential oil was mainly constituted of sesquiterpenes (54.1–55.0%) and oxygenated sesquiterpenoids (32.5–33.6%), the major constituents being: (E)-β-caryophyllene (24.1–25.0%), α-humulene (11.6–12.0%), caryophyllene oxide (9.3–10.9%), linalool (4.5–5.2%), humulene epoxide II (3.6–4.1%), (E)-nerolidol (3.7–4.0%), α-copaene (3.7–3.9%), α-muurolol (3.4–3.7%), α-selinene (3.4–3.5%), β-selinene (3.1–3.3%), and one undetermined oxygenated sesquiterpenoid (3.1–3.3%). The aqueous phase (hydrolate) of the distillation process was also submitted to chemical analysis, showing linalool as the main organic compound in solution, with a concentration of 12.3–15.7 mg/100 mL. The essential oil was than analyzed for the enantiomeric distribution of its monoterpene constituents, affording the following enantiomeric excesses in two β-cyclodextrin-based enantioselective columns: (1S,5S)-(-)-α-pinene (60.0–69.6%), (1S,5S)-(-)-β-pinene (5.2–7.2%), (R)-(-)-α-phellandrene (72.5–78.2%), (R)-(+)-limonene (28.6%) and (R)-(-)-linalool (1.8–3.1%).

Ethnopharmacology, phytochemistry and pharmacology of the genus Hedyosmum (Chlorantaceae): A review

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Hedyosmum (family: Chloranthaceae) represents an interesting source of natural active compounds, and the 45 species of this genus are widespread in Central and South America and to a lesser extent Southeast Asia (southern China and western Malaysia). Several species are traditionally used in folk medicine. However, the data made available in recent years have not been organized and compared.

AIM OF THIS REVIEW

The present study is a critical assessment of the state-of-the-art concerning the traditional uses, the phytochemistry and the pharmacology of species belonging to the genus Hedyosmum to suggest further research strategies and to facilitate the exploitation of the therapeutic potential of Hedyosmum species for the treatment of human disorders.

MATERIALS AND METHODS

The present review consists of a systematic overview of scientific literature concerning the genus Hedyosmum published between 1965 and 2018. Moreover, an older text, dated from 1843, concerning the traditional uses of H. bonplandianum Kunth has also been considered. Several databases (Francis & Taylor, Google Scholar, PubMed, SciELO, SciFinder, Springer, Wiley, and The Plant List Database) have been used to perform this work.

RESULTS

Sixteen species of the genus Hedyosmum have been mentioned as traditional remedies, and a large number of ethnomedicinal uses, including for the treatment of pain, depression, migraine, stomach-ache and ovary diseases, have been reported. Five species have been used as flavouring agents, tea substitutes or foods. Sesterterpenes, sesquiterpene lactones, monoterpenes, hydroxycinnamic acid derivatives, flavonoids, and neolignans have been reported as the most important compounds in these species. Studies concerning their biological activities have shown that members of the Hedyosmum genus possesses promising biological properties, such as analgesic, antinociceptive, antidepressant, anxiolytic, sedative, and hypnotic effects. Preliminary studies concerning the antibacterial, antioxidant, antiplasmodial, and antifungal activities of these plants as well as their cytotoxic activities against different tumour cell lines have been reported. Some active compounds from the Hedyosmum genus have been used as starting points for the innovative and bioinspired development of synthetic molecules. A critical assessment of these papers has been performed, and some conceptual and methodological problems have been identified regarding the materials and methods and the experimental design used in these studies, including a lack of ethnopharmacological research.

CONCLUSIONS

The present review partially confirms the basis for some of the traditional uses of Hedyosmum species (mainly H. brasiliense) through preclinical studies that demonstrated their antinociceptive and neuroprotective effects. Due to promising preliminary results, further studies should be conducted on 13-hydroxy-8,9-dehydroshizukanolide and podoandin. Moreover, several essential oils (EOs) from this genus have been preliminarily investigated, and the cytotoxic and antibacterial activities of H. brasiliense and H. sprucei EOs certainly deserve further investigation. From the promising findings of the present analysis, we can affirm that this genus deserves further research from ethnopharmacological and toxicological perspectives.

Chemical Composition, Enantiomeric Distribution, and Sensory Evaluation of the Essential Oils Distilled from the Ecuadorian Species Myrcianthes myrsinoides (Kunth) Grifo and Myrcia mollis (Kunth) DC. (Myrtaceae)

The essential oils of Myrcianthes myrsinoides and Myrcia mollis, belonging to the Myrtaceae family, were obtained by steam distillation. They were analyzed by gas chromatography-mass spectrometry (GC-MS), gas chromatography-flame ionization detector (GC-FID), enantioselective gas chromatography, and gas chromatography-olfactometry (GC-O). A total of 58 compounds for Myrcianthes myrsinoides essential oil (EO) and 22 compounds for Myrcia mollis EO were identified and quantified by GC-MS with apolar and polar columns (including undetermined components). Major compounds (>5.0%) were limonene (5.3%–5.2%), 1,8-cineole (10.4%–11.6%), (Z)-caryophyllene (16.6%–16.8%), trans-calamenene (15.9%–14.6%), and spathulenol (6.2%–6.5%). The enantiomeric excess of eight chiral constituents was determined, being (+)-limonene and (+)-germacrene D enantiomerically pure. Eight components were identified as determinant in the aromatic profile: α-pinene, β-pinene, (+)-limonene, γ-terpinene, terpinolene, linalool, β-elemene and spathulenol. For M. mollis, the major compounds (>5.0%) were α-pinene (29.2%–27.7%), β-pinene (31.3%–30.0%), myrcene (5.0%–5.2%), 1,8-cineole (8.5%–8.7%), and linalool (7.7%–8.2%). The enantiomeric excess of five chiral constituents was determined, with (S)-α-pinene and (+)-germacrene D enantiomerically pure. The metabolites β-pinene, 1,8-cineole, γ-terpinene, terpinolene, linalool, and (E)-β-caryophyllene were mainly responsible for the aroma of the EO. Finally, the M. myrsinoides essential oil has an inhibitory activity for cholinesterase enzymes (IC₅₀ of 78.6 μg/mL and 18.4 μg/mL vs. acethylcholinesterase (AChE) and butyrylcholinesterase (BChE) respectively). This activity is of interest to treat Alzheimer’s disease.