Synergistic terpene combinations as larvicides against the dengue vector Aedes aegypti Linn

Most of the essential oils (EO) known for mosquitocidal activity contain terpenes as part of their chemical constituents. In this study, four monoterpenes namely γ-terpinene (T), R-(+)-limonene (L), carvacrol (C), and trans-anethole (A) were screened against late third instar Aedes aegypti Linn. larvae singly and in combination to find out the synergistic interaction. The monoterpenes γ-terpinene, R-(+)-limonene, trans-anethole, and carvacrol showed larvicidal activity with LC₅₀ values of 9.76, 11.88, 50.19, 48.57 ppm and LC₉₀ values of 16.99, 17.78, 65.21, 75.02 ppm, respectively for Ae. aegypti when tested individually. Prepared binary combinations at LC₂₀ values and studied the synergistic interactions based on cotoxicity factor (CTF) and found that all the binary combinations showed synergistic interactions (CTF > 20). Further, the binary (1:1), ternary (1:1:1), and quaternary (1:1:1:1) terpene combinations on equal weight basis were prepared, evaluated against Ae. aegypti larvae and synergistic interactions were studied by Wadley's method. Among the eight combinations two combinations viz. LC (LC₅₀ 10.42 ppm) and LA (LC₅₀ 11.86 ppm) were showing synergistic interactions (R > 1.5) and others were exhibiting additive effect (1.5 ≥ R > 0.5) and none of the combinations showed antagonism (R < 0.5). Among the two methods used the Wadley's method found suitable when combinations were made on an equal weight basis. The two binary combinations found in this study are promising synergistic mixtures which has scope in designing mosquito larvicidal EOs by enriching the EOs with terpenes or by producing EO combinations with these terpenes as chemical constituents in the correct proportions.

Chemical Composition of the Essential Oil from Croton kimosorum, an Endemic Species to Madagascar

Croton kimosorum Leandri is an endemic species to Madagascar. The chemical composition of aerial parts, leaf and stem oils is reported for the first time. Analysis was carried out by combination of chromatographic (CC, GC), spectroscopic and spectrometric (MS, 13C NMR) techniques. In total, 76 compounds have been identified. Essential oil isolated from aerial parts contained mainly linalool (21.6%), sabinene (10.4%), 1,8-cineole (6.3%), β-pinene (6.2%), ( E)-P-caryophyllene (5.9%), terpinen-4-ol (4.8%), geraniol (4,5%) and germacrene D (2.3%). In comparison with the first sample, the composition of leaf and stem oils varied slightly, while essential oil isolated by vapor distillation from a semi-industrial still exhibited similar composition.

Cardiovascular Effects of the Essential Oil of Croton Zehntneri Leaves in DOCA-salt Hypertensive, Conscious Rats

This study investigated the cardiovascular effects of the essential oil of Croton zehntneri (EOCZ) in deoxycorticosterone-acetate (DOCA)-salt hypertensive rats. Furthermore, in vitro experiments using isolated thoracic aortic rings were performed to assess the vascular effects of the EOCZ. In conscious hypertensive rats, intravenous (i.v.) injections of EOCZ (1–20 mg/kg) induced rapid (2–4 s) and dose-dependent hypotension and bradycardia (phase 1). The hypotension was followed by a significant pressor effect that was more evident at the higher doses (10 and 20 mg/kg) of EOCZ. Hypotension and bradycardia of EOCZ (phase 1) were abolished and respectively reversed into pressor and tachycardiac effects by methylatropine (1 mg/kg, i.v.) pretreatment. In isolated endothelium-intact aortic preparations, increasing concentrations (1–1000 μg/mL) of EOCZ relaxed the potassium-induced contraction in a concentration-dependent manner with an IC50 (geometric mean [95% confidence interval]) value of 202.0 [92.0–443.7] μg/mL. This vasorelaxant effect remained unaffected by either mechanical removal of functional vascular endothelium (IC50 = 189.0 [159.4–224.7] μg/mL) or the addition of atropine (1 μM) (IC50 = 158.6 [79.8–316.2] μg/mL) in the perfusion medium. These data show that i.v. administration of EOCZ in DOCA-salt hypertensive rats induces a vago-vagal reflex decreases in heart rate and blood pressure (phase 1). EOCZ may induce a second and delayed hypotension due to its direct endothelium-independent vasorelaxant effects, but it seems to be buffered by the pressor component (subsequent to phase 1) of EOCZ. This pattern of blood pressure and heart rate responses to EOCZ seems unaltered by DOCA-salt hypertension, as was similar to that previously reported in conscious normotensive rats.

Essential Oil of Croton Argyrophylloides: Toxicological Aspects and Vasorelaxant Activity in Rats

Croton argyrophylloides Muell. Arg. is widely used in Brazilian folk medicine to treat diabetes and venereal diseases. This study examined the acute toxicity and cytotoxicity of the essential oil of C. argyrophylloides(EOCA). In addition, vascular effects of the EOCA have been examined. In mice, an oral acute toxicity test revealed that EOCA could be considered as a non toxic essential oil since it showed a very high LD50 (9.84 ± 0.01 g/kg). In the brine shrimp ( Artemia salina) cytotoxic assay, the LC50 value of EOCA was 275 [165-534] μg/mL. EOCA (1-1000 μg/mL) relaxed isolated endothelium-intact aortic rings precontracted with phenylephrine with an IC50 value of 126.7 [89.8-163.7] μg/mL. In rat mesenteric bed preparations precontracted with phenylephrine, EOCA (1-300 μg/mL) also induced a reversible, vasodilator effect with an IC50 value of 46.0 [33.3-58.7] μg/mL. It is concluded that EOCA is a very interesting agent from the point of view of the possibility of therapeutic application. This is because, whilst showing a very small acute toxicity, EOCA also showed maximal efficacy as a vascular antispasmodic agent with a pharmacological potency similar to that of other Croton species essential oils.

Acaricidal Activity against Tetranychus Urticae and Essential Oil Composition of Four Croton Species from Caatinga Biome in Northeastern Brazil

Volatile components of essential oils from the leaves and stems of Croton jacobinensis, C. rhamnifolius, C. muscicapa and C. micans, which are medicinal plants found in the Caatinga biome of northeastern Brazil, were analyzed using GC and GC/MS. The acaricidal activity of these oils against Tetranychus urticae was evaluated using the fumigation method. Oil yields from the Croton species ranged from 1.1±0.0 to 0.6±0.0%, w/w, for leaves and 0.7±0.0 to 0.1±0.0% for stems. Sesquiterpenoids were dominant in all oils, except the stem oil from C. rhamnifolius, which exhibited a high monoterpene content, and the leaf and stem oils from C. muscicapa, which were rich in phenylpropanoids. The major volatile components of the leaf and stem oils from C. jacobinensis were ( Z)-α-atlantone (24.3±0.4%) and trans-isolongifolanone (22.8±0.5%), respectively. The most abundant constituents detected in C. rhamnifolius were #aL-cedrene epoxide (23.3±0.1%) and caryophyllene oxide (21.9±0.0%) in the leaf oil, and camphor (16.6±0.5%) and tricyclene (12.8±0.1%) in the stem oil. Foenicolin was the main compound identified in the leaf (50.6±0.2%) and stem (72.7±0.6%) oils of C. muscicapa, while α-bulnesene (32.9±0.2%) and guaiol (17.9±0.7%) were the principal components of C. micans oils. These oils exhibited a high degree of toxicity in the fumigation assay. The stem oils from C. jacobinensis and C. rhamnifolius exhibited high lethality rates, with LC50 values of 0.3 and 0.2 μL/L of air after 24 h, respectively. The results suggest the potential use of stem essential oil, especially from C. rhamnifolius and C. jacobinensis, for the integrated control of Tetranychus urticae.

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 α-cedrene oxide (18.6%), spathulenol (16.3%), valencene (5.8%), geranyl-pentanoate (5.3%), α-cadinol (4.0%), germacrene D (3.5%) and longifolene (3.3%).

Chemical Constituents and Larvicidal Activity of Hymenaea courbaril Fruit Peel

The chemical compositions of the essential oils from the peel of ripe and unripe fruits of Hymenaea courbaril L., obtained by hydrodistillation, were analyzed by GC and GC-MS. The main constituents of the essential oil from the peel of the ripe fruits were the sesquiterpenes α-copaene (11.1%), spathulenol (10.1%) and β-selinene (8.2%), while germacrene-D (31.9%), β-caryophyllene (27.1%) and bicyclogermacrene (6.5%) were the major compounds in the oil from unripe fruits. The essential oils were tested against Aedes aegypti larvae and showed LC50 values of 14.8 ± 0.4 μg/mL and 28.4 ± 0.3 μg/mL for the ripe and unripe fruit peel oils, respectively. From the peel of the ripe fruits, the diterpenes zanzibaric acid and isoozic acid were isolated, along with the sesquiterpene caryolane-1,9β-diol. To the best of our knowledge, this is the first report of this sesquiterpene in the genus. The structures of all compounds isolated were identified on the basis of their spectral data (IR, MS, 1D- and 2D-NMR) and by comparison with literature spectral data.

Magnoflorine and Phenolic Derivatives from the Leaves of Croton xalapensis L. (Euphorbiaceae)

The alkaloid magnoflorine 1, has been isolated for the first time from Croton xalapensis (Euphorbiaceae), in addition two phenylpropenols derivates, 3,4-dimethoxy-(E)-cinnamyl alcohol 2 and 3,4-dimethoxy-5-hydroxy-(E)-cinnamyl alcohol 3, 3,4,5-trimethoxycinnamic acid 4, gallic acid 5, methyl gallate 6 and 3,4-dihydroxybenzoic acid 7 have been also found; these compounds were identified by spectroscopic analysis particularly, 2D NMR and ESI-MS/MS techniques. The high concentration of magnoflorine, calculated with quantitative HPLC, of the aqueous extract, probably contributes to the remarkable medicinal properties of this plant. In addition this is the first phytochemical study on Croton xalapensis to be reported.

Essential Oils and Anxiolytic Aromatherapy

A number of essential oils are currently in use as aromatherapy agents to relieve anxiety, stress, and depression. Popular anxiolytic oils include lavender (Lavandula angustifolia), rose (Rosa damascena), orange (Citrus sinensis), bergamot (Citrus aurantium), lemon (Citrus limon), sandalwood (Santalum album), clary sage (Salvia sclarea), Roman chamomile (Anthemis nobilis), and rose-scented geranium (Pelargonium spp.). This review discusses the chemical constituents and CNS effects of these aromatherapeutic essential oils, as well as recent studies on additional essential oils with anxiolytic activities.