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.

Onoseriolide, from Hedyosmum racemosum, induces cytotoxicity and apoptosis in human colon cancer cells.

The number of colon cancer patients is increasing, and new alternatives for treatment are important. We focused on the sesquiterpene lactone onoseriolide from Hedyosmum racemosum, which is widely used in traditional medicine. This compound was evaluated to determine its cytotoxic effect and the mechanism of cell death that is induced in the human colon cancer cell line RKO. A dose-dependent decrease in cell viability was observed. p53 expression increased followed by an increase in p21 expression, which is involved in cell cycle arrest in the G2/M phase. Caspase-3 activation and PARP-1 cleavage, which are apoptotic markers, were also monitored. Autophagy markers were also studied, and Beclin 1 was downregulated, while LC-3II increased in a dose-dependent manner. There were no changes in SQSTM1/p62 regulation. Onoseriolide exerts cytotoxic and cytostatic effects, activating the autophagy pathway as a protective mechanism and apoptosis as the cell death pathway.

Essential oil composition and cytotoxic activity in twospecies ofthe plant genus Vismia (Hypericaceae) from the Venezuelan Andes / Composición de aceites esenciales y actividad citotóxica en dos especies de plantas del género Vismia (Hypericaceae) de los Andes venezolanos

Introduction: The Vismia genus belongs to the Hypericaceae family and comprises around 57 species of which 17 have been located in Venezuela. Previous investigations have been carried out in extracts as well as pure isolated compounds, revealing antimicrobial, antioxidant and anti-HIV, among other, biological activities. Objective: This investigation aims to determine the cytotoxic activity of essential oils from leaves of Vismia baccifera Triana & Planch (VBJ and VBV) and Vismia macrophylla Kunth (VM) collected in three different locations of the Venezuelan Andean region. Methods: Essential oils obtained by hydrodistillation were analyzed using gas chromatography-mass spectrometry (GC-MS) and their cytotoxic activity was analyzed following the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. Human tumor cell lines from SKBr3, MCF-7 and PANC-1, two breast carcinomas and one pancreatic adenocarcinoma of ductal type, were tested with the oil samples and human dermis fibroblasts were used as non-tumor cells. Results: β-caryophyllene and trans-caryophyllene were present as major components in VBJ and VBV, respectively, while γ-bisabolene was the main component in the VM sample. Anticancer activity was observed on V. baccifera essential oil against SKBr3, MCF-7 and PANC-1. The selectivity index showed that VBV is highly selective against the SKBr3 cell line and has no activity against non-tumor cells. Conclusions: These results are considered a contribution to natural products research and may provide supportive data for future studies on cancer.

Introducción: El género Vismia pertenece a la familia Hypericaceae y comprende alrededor de 57 especies de las cuales 17 han sido ubicadas en Venezuela. Se han realizado investigaciones previas tanto en extractos como en compuestos puros aislados revelando actividad antimicrobiana, antioxidante y anti-VIH, entre otras actividades biológicas. Objetivo: El propósito de esta investigación es determinar la actividad citotóxica de los aceites esenciales de las hojas de Vismia baccifera Triana & Planch (VBJ y VBV) y Vismia macrophylla Kunth (VM) recolectadas en tres localidades de la región andina venezolana. Métodos: Aceites esenciales obtenidos por hidrodestilación fueron analizados por cromatografía de gases-espectrometría de masas y su actividad citotóxica fue analizada siguiendo el método MTT (bromuro de 3-[4,5-dimetiltiazol-2-il]-2,5-difeniltetrazolio). Los aceites esenciales fueron ensayados frente a células tumorales humanas SKBr3, MCF-7 y PANC-1, dos carcinomas de mama y un adenocarcinoma pancreático del tipo ductal, usando cultivos primarios de fibroblastos de dermis humana como células no tumorales. Resultados: β-cariofileno y trans-cariofileno estuvieron presentes como compuestos mayoritarios en VBJ y VBV, respectivamente, mientras que γ-bisaboleno fue el componente principal en la muestra VM. El aceite esencial de V. baccifera mostró actividad anticancerígena frente a SKBr3, MCF-7 y PANC-1. El índice de selectividad reveló que VBV es altamente selectivo frente a la línea celular SKBr3 y no presenta actividad contra las células no tumorales. Conclusiones: Estos resultados se consideran una contribución a la investigación de los productos naturales y los datos pueden ser de utilidad en futuras investigaciones sobre el cáncer.

Cytotoxic Property of Grias neuberthii Extract on Human Colon Cancer Cells: A Crucial Role of Autophagy.

Traditional herbal medicine has become an important alternative in the treatment of various cancer types, including colon cancer, which represents one of the main health problems around the world. Therefore, the search for new therapies to counteract this disease is very active. Grias neuberthii is an endemic plant located in the Ecuadorian Amazon region, which has been used in traditional medicine for its pharmacological properties, including its ability to inhibit tumor cell growth, although scientific studies are limited. We have analyzed the effect of this plant on two colon carcinoma cell lines, that is, RKO (normal p53) and SW613-B3 (mutated p53) cells. Among several extracts obtained from various parts of G. neuberthii plant, we identified the extract with the greatest cytotoxic potential, derived from the stem bark. The cytotoxic effect was similar on both cell lines, thus indicating that it is independent of the status of p53. However, significant differences were observed after the analysis of colony formation, with RKO cells being more sensitive than SW613-B3. No evidence for apoptotic markers was recorded; nevertheless, both cell lines showed signs of autophagy after the treatment, including increased Beclin-1 and LC3-II and decreased p62. Finally, three chemical compounds, possibly responsible for the effect observed in both cell lines, were identified: lupeol (1), 3'-O-methyl ellagic acid 4-O-ß-D-rhamnopyranoside (2), and 19-α-hydroxy-asiatic acid monoglucoside (3).

α-Glucosidase Inhibition and Antibacterial Activity of Secondary Metabolites from the Ecuadorian Species Clinopodium taxifolium (Kunth) Govaerts.

The phytochemical investigation of both volatile and fixed metabolites of Clinopodium taxifolium (Kunth) Govaerts (Lamiaceae) was performed for the first time. It allowed the isolation and characterization of the essential oil and six known compounds: carvacrol (1), squalane (2), uvaol (3), erythrodiol (4), ursolic acid (5), and salvigenin (6). Their structures were identified and characterized by Nuclear Magnetic Resonance (NMR) and Gas Chromatography coupled to Mass Spectroscopy (GC-MS), and corroborated by literature. The essential oil of the leaves was obtained by hydrodistillation in two different periods and analyzed by GC-MS and GC coupled to Flame Ionization Detector (GC-FID). A total of 54 compounds were detected, of which 42 were identified (including trace constituents). The major constituents were carvacrol methyl ether (18.9-23.2%), carvacrol (13.8-16.3%) and, carvacryl acetate (11.4-4.8%). The antibacterial activities were determined as Minimum Inhibition Concentration (MIC) against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, Pseudomonas aeruginosa and Micrococcus luteus. The hexane and methanol extracts exhibited activity only against Klebsiella pneumoniae (250 and 500 µg/mL respectively), while the ethyl acetate extract was inactive. The hypoglycemic activity was evaluated by the in vitro inhibition of α-glucosidase. The ethyl acetate (EtOAc) extract showed strong inhibitory activity with IC50 = 24.88 µg/mL, however methanolic and hexanic extracts showed weak activity. As a pure compound, only ursolic acid showed a strong inhibitory activity, with IC50 = 72.71 µM.

The role of the glycosyl moiety of myricetin derivatives in anti-HIV-1 activity in vitro.

BACKGROUND: Plant extracts are sources of valuable compounds with biological activity, especially for the anti-proliferative activity against pathogens or tumor cells. Myricetin is a flavonoid found in several plants that has been described as an inhibitor of Human immunodeficiency virus type 1 (HIV-1) through its action against the HIV reverse transcriptase, but myricetin derivatives have not been fully studied. The aim of this study was to evaluate the anti-HIV-1 activity of glycosylated metabolites obtained from Marcetia taxifolia and derived from myricetin: myricetin rhamnoside and myricetin 3-(6-rhamnosylgalactoside). METHODS: Compounds were obtained from organic extracts by maceration of aerial parts of M. taxifolia. All biological assays were performed in the MT4 cell line. Antiviral activity was measured as inhibition of p24 and reverse transcriptase with a fluorescent assay. RESULTS: Both flavonoids have antiviral activity in vitro, with an EC50 of 120 µM for myricetin 3-rhamnoside (MR) and 45 µM for myricetin 3-(6-rhamnosylgalactoside) (MRG), both significantly lower than the EC50 of myricetin (230 µM). Although both compounds inhibited the reverse transcriptase activity, with an IC50 of 10.6 µM for MR and 13.8 µM for MRG, myricetin was the most potent, with an IC50 of 7.6 µM, and an inhibition greater than 80%. Molecular docking approach showed correlation between the free energy of binding with the assays of enzyme inhibition. CONCLUSIONS: The results suggest that glycosylated moiety might enhance the anti-HIV-1 activity of myricetin, probably by favoring the internalization of the flavonoid into the cell. The inhibition of the HIV-1 reverse transcriptase is likely responsible for the antiviral activity.

Main Constituents and Antidiabetic Properties of Otholobium mexicanum.

Two phenols, bakuchiol (1) and 3-hydroxybakuchiol (2), and two isoflavone glycosides, daidzin (3) and genistin (4) were isolated from Otholobium mexicanum J. W. Grimes (Fabaceae). Moreover, the ability of the raw extract and isolated metabolites to inhibit the enzymes α-amylase and α-glucosidase was evaluated in vitro. In the α-amylase assay, the methanolic extract exhibited a moderate inhibitory activity with an IC50 of 470 µg/mL, while inhibition percentages of bakuchiol (1), 3-hydroxybakuchiol (2), and daidzin (3) were less than 25% at the maximum dose tested (1 µM). Genistin (4) exhibited a poor activity with an IC50 of 805 µM. In the α-glucosidase assay, the methanolic extract exhibited a strong inhibitory activity with an IC50 value of 32 µg/mL, while 3-hydroxybakuchiol (2) exhibited a moderate inhibitory activity with an IC50 of 345 µM. Daidzin (3) and genistin (4) exhibited lower inhibitory activity with IC50 values of 564 µM and 913 µM, respectively. Bakuchiol (1) exhibited a poor inhibitory activity with an inhibition percentage less than 10% at the maximum dose tested (1 mM).

A new indole-alkaloid and a new phenolic-glycoside with cytotoxic activity from Strychnos fendleri.

A new indole alkaloid strychnosinol (1) and a new phenolic-glycoside (2) were isolated from the bark and leaves of Strychnos fendleri Sprague & Sandwith, together with six known compounds reported for the first time in this species. The structures of these compounds were determined on the basis of spectroscopic data; mainly those obtained by using (1)H and (13)C NMR (1D and 2D) and mass spectrometry. Strychnosinol (1) and the phenolic glycoside (2) together with compounds 3-8 were evaluated for cytotoxicity against a panel of five tumour cell lines; IC50 values between 0.090 and 0.227 µM for the human tumour cell lines were observed for compound 2.

New 3,4-seco-ent-kaurene dimers from Croton micans.

From the stems of Croton micans Sw., five new 3,4-seco-ent-kaurene dimers: micansinoic acid (1), isomicansinoic acid (2), and the dimethyl (3), monomethyl (4) and monoethyl ester (5) of micansinoic acid were isolated. The structures of the new compounds were elucidated by spectroscopic data interpretation, mainly 1D and 2D NMR experiments and MS. These compounds are the first 3,4-seco-ent-kaurene dimers from a Croton species.

Chemical composition of the essential oil of Croton gossypiifolius from Venezuela.

The essential oil from leaves of Croton gossypiifolius Vahl. (Euphorbiaceae) was obtained by hydrodistillation, and analyzed by GC/FID and GC/MS. The constituents were identified by their mass spectra and Kovats' indices. Fifty-one compounds accounting for 92% of the oil were detected, and 47 of them were identified. The oil was dominated by oxygenated sesquiterpenes with the major presence of alpha-cedrene oxide (18.6%), spathulenol (16.3%), valencene (5.8%), geranyl-pentanoate (5.3%), alpha-cadinol (4.0%), germacrene D (3.5%) and longifolene (3.3%).

Cytotoxic activity of seco-entkaurenes from Croton caracasana on human cancer cell lines.

In the course of searching for bioactive compounds from Croton species from Venezuela, two seco-entkaurenes isolated from flowers of Croton caracasana were evaluated in vitro for their effect on cell viability by the standard MTT assay in nine human cancer cell lines of different origins and one primary culture. Both compounds induced cytotoxicity in the range of 2 to 25 microM for caracasine and 0.8 to 12 microM for caracasine acid. However, for the normal fibroblasts and the cell lines, HeLa, MCF-7, PC-3, LoVo, X-17, Jurkat E6.1 and Jurkat JCaM1.6, the IC50 values of caracasine acid were lower than their counterparts. Interestingly, no differences in IC50 were recorded for the leukemic cell lines U937 and K562. It can be concluded that the acid moiety in the structure enhances the cytotoxic effect of caracasine by a pathway which seems not to be activated in the leukemic cell lines tested.

Hypoglycaemic effect of Croton cuneatus in streptozotocin-induced diabetic rats

Aqueous extract of the stem barks of Croton cuneatus Klotz (Euphorbiaceae) was investigated for hypoglycaemic activity in streptozotocin(STZ)-induced diabetic rats. Increasing doses of aqueous extract (6.5, 13, 26 and 52 mg/kg i.p.) were separately administered to groups of fasted normal and diabetic rats. Plasma glucose concentration, cholesterol and changes in body weight were evaluated. The chronic intraperitoneal (i.p.) administration of the extract for 22 days was found to induce significant reduction in blood glucose level. A comparison was made between the action of the aqueous extract of C. cuneatus and the reference standard drug glibenclamide. The results of this experimental animal study indicate that this plant has an antidiabetic activity in hiperglycaemic rat models.

A ação hipoglicemiante do extrato aquoso das cascas do caule de Croton cuneatus Klotz (Euphorbiaceae) foi investigada em ratos com diabetes induzida pela estreptozotocina (STZ). Doses crescentes do extrato aquoso (6,5, 13, 26 e 52 mg/kg i.p.) foram administradas separadamente a grupos de animais normais e diabéticos em jejum. Foram avaliadas as concentrações plasmáticas de glicose e colesterol, assim como mudanças no peso corporal. A administração crônica intraperitoneal (i.p.) do extrato durante 22 dias induziu uma redução significativa nos níveis de glicose sanguínea. Foi feita uma comparação entre o extrato aquoso de C. cuneatus e a droga de referência glibenclamida. Os resultados desse experimento indicam que esta planta possui atividade antidiabética em modelo com animais hiperglicêmicos.

Anti-inflammatory activity of Croton cuneatus aqueous extract.

The aqueous extract of Croton cuneatus Klotz. (Euphorbiaceae), was tested for its antinociceptive effects using chemical and thermal test models in mice. Anti-inflammatory activity was determined in Sprague-Dawley rats in a model of acute plantar inflammation induced by bovine serum albumin. Croton cuneatus aqueous extract at doses of 7 mg/kg showed a significant anti-inflammatory effect compared with commonly used non-stereoidal drugs as ketoprofen, sodium diclofenac and ASA (acetylsalicylic acid).

Three new glutarimide alkaloids from Croton cuneatus.

Analysis of the dichloromethane extract of the aerial parts of Croton cuneatus led to the isolation of the new glutarimide alkaloids: julocrotol (1), isojulocrotol (2), and julocrotone (3) along with the known compounds julocrotonine (4), lichexanthone (5) and selin-11-en-4alpha-ol (6). The structures of the new compounds were established by spectral methods. The in vitro cytotoxic activity of Compounds 1-6 was evaluated against six human tumor cells lines.

Antinociceptive and anti-inflammatory effects of Croton malambo bark aqueous extract.

Croton malambo (K.) bark aqueous extract, popularly known in Venezuela as "palomatias" or "torco" was tested for acute toxicity and for its anti-inflammatory and antinociceptive effects using tail flick and writhing syndrome tests models, respectively. Croton malambo aqueous extract (6.15 mg/kg i.p.) administered intraperitoneally had a significant antinociceptive and anti-inflammatory effects compared to acetylsalicylic acid (200mg/kg p.o.) and sodium diclofenac (5.64 mg/kg p.o.). Studies to determine correlation between chemical composition and pharmacological activity are underway.

Biflavonoids from Podocalyx loranthoides.

Analysis of the ethyl acetate extract of the aerials parts of Podocalyx loranthoides led to the isolation of I 7, II 4'-dimethylamentoflavone (1) and II 4'-methylamentoflavone (2). Compound (1) gave a moderate effect against Leishmania mexicana promastigotes.