Exploration of essential oil from Psychotria poeppigiana as an anti-hyperalgesic and anti-acetylcholinesterase agent: Chemical composition, biological activity and molecular docking

ETHNOPHARMACOLOGICAL RELEVANCE

Leaves from Psychotria poeppigiana Müll. Arg. (accepted as Palicourea tomentosa (Aubl.) Borhidi), Rubiaceae, has traditionally been used in medicine for treatments of inflammation and pain; Synonymously, Cephaelis elata for the treatment of dementia; However, few scientific studies have been evidence demonstrating this activity.

AIM OF THE STUDY

The aim of this study was to investigate the chemical composition of P. poeppigiana essential oil obtained from leaves (EOPP) and its antioxidant, anti-inflammatory and acetylcholinesterase (AChE) activities. Molecular docking simulations were carried out with the main constituents.

MATERIALS AND METHODS

EOPP (hydrodistillation) was analysed by gas chromatography-mass spectrometry (GC-MS). The fractionation of EOPP afforded germacrene D and bicyclogermacrene. The antioxidant activity of EOPP was determined by MDA assay. The inflammatory parameters were evaluated using CFA model (with paw edema, mechanical, thermal hyperalgesia, MPO and NAG) in EOPP (30, 100 and 300 mg/kg), germacrene D and bicyclogermacrene (30 mg/kg). The AChE inhibition was evaluated in rat brain structures and molecular docking simulations were carried out using Autodock v.4.3.2.

RESULTS

GC-MS analysis identified 19 compounds, and the major compounds were germacrene D (29.38%) and bicyclogermacrene (25.21%). EOPP exhibited high antioxidant capacity (IC₅₀ = 12.78 ± 1.36 μg/mL). All the tested doses of EOPP and both major constituents significantly inhibited cold and mechanical hyperalgesia and significantly blocked the increase in MPO activity 24 h after the CFA injection. There was significant AChE inhibition by EOPP and germacrene D in the cerebral cortex and hippocampus (>50%). Enzyme-ligand molecular modelling showed that the major constituents of EOPP interacted differently with AChE.

CONCLUSIONS

The chemical compounds of the essential oil from the leaves of P. poeppigiana is based mainly on terpenes, the sesquiterpenes germacrene D (29.38%) and bicyclogermacrene (25.21%) being the major compounds. EOPP presented antioxidant, anti-inflammatory and anti-acetylcholinesterase (AChE) activities. Besides, enzyme-ligand molecular modelling showed the EOPP may act as an anti-hyperalgesic and AChE inhibitory agent. Taken together, these results might be in accordance with if folk use for pain- and inflammation-related symptoms.

(Rubiaceae) stem bark methanol extract contributes to its antiepileptogenic activity against pentylenetetrazol kindling in male Wistar rats

A substantial number of epileptic patients are resistant to the current medication thus necessitating the search for alternative therapies for intractable forms of the disease. Previous studies demonstrated the acute anticonvulsant properties of the methanol extract of the stem bark of Psychotria camptopus (MEPC) in rats. This study investigated the effects of MEPC on pentylenetetrazole-kindled Wistar rats. Kindling was induced by intraperitoneal injection of pentylenetetrazole (37.5 mg/kg) on every alternate day, 1 h after each daily oral pretreatment of rats (8 ≤ n ≤ 10) with MEPC (40, 80 and 120 mg/kg), vehicle or diazepam (3 mg/kg) for 43 days. The kindling development was monitored based on seizure episodes and severity. Rats' brains were collected on day 43 for the determination of oxidative stress parameters. The histomorphological features and neuronal cell viability of the prefrontal cortex (PFC) and hippocampus were also assessed using H&E and Cresyl violet stains. Chronic administration of pentylenetetrazole time-dependently decreased the latency to myoclonic and generalized seizures, and increased seizure scores and the number of kindled rats. MEPC and diazepam significantly increased the latencies to myoclonic jerks and generalized tonic-clonic seizures. These substances also reduced seizure score and the number of rats with PTZ-kindling. MEPC improved glutathione status and decreased lipid peroxidation in the brains of kindled rats. MEPC also exhibited neuroprotection against pentylenetetrazole-induced hippocampal and PFC neuronal damages. These results suggest that P. camptopus has antiepileptogenic activity, which might be related to the augmentation of antioxidant and neuroprotective defense mechanisms, and further confirm its usefulness in the management of epilepsy.

In vitro antiplasmodial activity, targeted LC-MS metabolite profiling, and identification of major natural products in the bioactive extracts of Palicourea and Psychotria species from the Amazonia and Atlantic Forest biomes, Brazil

INTRODUCTION

A great variety of bioactive natural products has been reported for different Palicourea and Psychotria species (Rubiaceae). However, few of them as well as few of species of these botanical genera have been evaluated for antiplasmodial activity.

OBJECTIVE

To assess the antiplasmodial activity of 24 extracts from Palicourea and Psychotria genera, along with the targeted LC-MS metabolite profiling, as well as identification of the main metabolites in the bioactive extracts.

METHODS

Twenty four ethanol and acid-base extracts from Palicourea and Psychotria genera collected in the Amazonia and Atlantic Forest, Brazil, were evaluated against chloroquine-resistant Plasmodium falciparum W2 strain by PfLDH. The metabolite profiling and putative identification of metabolites from bioactive extracts were determined by LC-DAD-ESI-MS and LC-HRMS, respectively.

RESULTS

The ethanol extracts disclosed low antiplasmodial activity (% GI < 50%). High antiplasmodial effect was observed for the acid-base extracts from Psychotria apoda and Psychotria colorata with 100% inhibition of parasite growth inhibition. Fragment ions related to pyrrolidinoindoline alkaloids were observed by LC-DAD-ESI-MS mainly in the most bioactive extracts. The results of the in vitro screening associated with the LC-DAD-ESI-MS and LC-HRMSⁿ data allowed to predict, for the first time, the pyrrolidinoindoline alkaloids as possible antiplasmodial representing, then, new potential natural antimalarial hits. In addition, other metabolite classes such as flavanones, lignans and chalcones were also putatively identified in the bioactive extracts of Psychotria apoda, Psychotria capitata, and Psychotria poeppigiana.

CONCLUSION

The present results point to Palicourea and Psychotria species as sources of new antimalarial hits.

Understory and canopy additions of nitrogen differentially affect carbon and nitrogen metabolism of Psychotria rubra in an evergreen broad-leaved forest

To assess the effects of nitrogen deposition on forest plants, researchers have conducted many nitrogen-addition experiments. Most of these experiments, however, failed to fully simulate atmospheric nitrogen deposition because they failed to assess interception of nitrogen deposition by the forest canopy. Here, we used transcriptomics, proteomics, and metabolomics to compare the effects of understory nitrogen addition (UAN), canopy nitrogen addition (CAN), and a control (no nitrogen addition) on carbon and nitrogen metabolism in leaves of Psychotria rubra, a dominant subtropical understory plant species in evergreen broad-leaved forests in South China. We first established a reference P. rubra transcriptome via RNA-seq and obtained a total of 93,986 unigenes from de novo assembly. Next, we quantitatively investigated the proteome and metabolome in leaves, and identified 4021 proteins and 562 metabolites. Under the CAN treatment and relative to the control, 36 genes were up-regulated and 23 were down-regulated, and we identified 46 up-regulated proteins and 49 down-regulated proteins. Under the UAN treatment and relative to the control, 1525 genes were up-regulated and 224 genes down-regulated, and we identified 35 up-regulated proteins and 71 down-regulated proteins. These differentially expressed genes and proteins were related to photosynthesis, amino acid metabolism, and flavonoid biosynthesis. Accordingly, 15 differentially accumulated metabolites in response to CAN and 20 in response to UAN were found; these differentially accumulated metabolites included 4 amino acids and 3 flavonoids. Taken together, our results show that the UAN treatment had a greater effect on photosynthesis, amino acid metabolism, and flavonoid biosynthesis than the CAN treatment. Most importantly, the results indicate that understory application of nitrogen in experiments may incorrectly estimate the effects of nitrogen deposition on nitrogen and carbon utilization by P. rubra and perhaps by other understory woody plants in the evergreen broad-leaved forests in South China as well.

Phylogenetic and geographic distribution of nickel hyperaccumulation in neotropical Psychotria

PREMISE

Hyperaccumulation of heavy metals in plants has never been documented from Central America or Mexico. Psychotria grandis, P. costivenia, and P. glomerata (Rubiaceae) have been reported to hyperaccumulate nickel in the Greater Antilles, but they also occur widely across the neotropics. The goals of this research were to investigate the geographic distribution of hyperaccumulation in these species and explore the phylogenetic distribution of hyperaccumulation in this clade by testing related species.

METHODS

Portable x-ray fluorescence (XRF) spectroscopy was used to analyze 565 specimens representing eight species of Psychotria from the Missouri Botanical Garden herbarium.

RESULTS

Nickel hyperaccumulation was found in specimens of Psychotria costivenia ranging from Mexico to Costa Rica and in specimens of P. grandis from Guatemala to Ecuador and Venezuela. Among related species, nickel hyperaccumulation is reported for the first time in P. lorenciana and P. papantlensis, but no evidence of hyperaccumulation was found in P. clivorum, P. flava, or P. pleuropoda. Previous reports of hyperaccumulation in P. glomerata appear to be erroneous, resulting from taxonomic synonymy and specimen misidentification.

CONCLUSIONS

Hyperaccumulation of nickel by Psychotria is now known to occur widely from southern Mexico through Central America to northwestern South America, including some areas not known to have ultramafic soils. Novel aspects of this research include the successful prediction of new hyperaccumulator species based on molecular phylogeny, use of XRF technology to nondestructively obtain elemental data from herbarium specimens, and documentation of previously unknown areas of ultramafic or nickel-rich soil based on such data.

[Chemical constituents from stems and leaves of Psychotria serpens]

The chemical consituents from the stems and leaves of Psychotria serpens were separated and purified by column chromatographies with silica gel, ODS, Sephadex LH-20 and PR-HPLC. The structures of the isolated compounds were identified on the basis of physicochemical properties and spectroscopic analyses, as well as comparisons with the data reported in literature. 18 compounds were isolated from the 90% ethanol extract of the stems and leaves of P. serpens, which were identified as chrysin(1), acacetin(2), genkwanin(3), chrysoeriol(4), rhamnocitrin(5), isorhamnetin(6), tricin(7), jaceosidin(8), dillenetin(9), kumatakenin(10), ayanin(11), isosakuranetin(12), eriodictyol(13), homoeriodictyol(14), taxifolin(15), pomonic acid(16), fupenzic acid(17) and euscaphic acid(18). All compounds were isolated from the genus Psychotria for the first time.

Pollen preference for Psychotria sp. is not learned in the passion flower butterfly, Heliconius erato

Heliconius butterflies are known to maximize fitness by feeding on pollen from Gurania sp. and Psiguria sp. (Cucurbitales: Curcurbitaceae), and Psychotria sp. (Gentianales: Rubiaceae). This specialization involves specific physical, physiological, and behavioral adaptations including efficient search strategies in the forest to locate pollen host plants, pollen removal, and pollen external digestion. Reducing pollen host plant search time is crucial to out-compete other flower visitors and to reduce exposure to predators. One way in which this can be achieved is by using chemical cues to learn from experienced foragers in roosting aggregations. Similar strategies have been documented in bumblebees, where inexperienced individuals learn floral odors from experienced foragers. Behavioral experiments using plants preferred by Heliconius erato suggest that pollen preference in H. erato is an innate trait and consequently learning of chemical cues at roosting aggregations is unlikely.

Potential bird dispersers of Psychotria in a area of Atlantic forest on Ilha Grande, RJ, Southeastern Brazil: a biochemical analysis of the fruits

The present study assessed the fruiting pattern, bird foraging behavior, and sugar content of ripe fruits of two sympatric species of Rubiaceae (Psychotria brasiliensis and P. nuda). This study was carried out in an Atlantic forest area on Ilha Grande, RJ, between August 1998 and July 1999. Fruit production occurred year round, with a peak of mature P. brasiliensis fruits in December 1998 and another of P. nuda in February of 1999. Lipaugus lanioides (Cotingidae), Baryphtengus ruficapillus (Momotidae) and Saltator similis (Emberizidae) made the most frequent foraging visits to fruiting P. brasiliensis, so that L. lanioides and B. ruficapillus removed the fruits with sallying maneuvers while S. similis gleaned the fruits. Lipaugus lanioides was by far the most important consumer, and potentially the main disperser of P. brasiliensis. Birds of this genus are heavy frugivores in the tropical forests and are widely assumed to be important seed dispersers. The fruits were analyzed quantitatively and qualitatively in relation to the amounts of sucrose and starch. Psychotria brasiliensis (the visited species) showed the smallest quantity of sucrose and the highest amount of starch. These findings suggest that what may influence the birds' choice of fruit is the proportion of starch in the Psychotria species studied here rather than the carbohydrate composition.

ENDOPHYTE OF PSYCHOTRIA BACTERIOPHILA

Centifanto, Ysolina M. (University of Florida, Gainesville), and Warren S. Silver. Leafnodule symbiosis. I. Endophyte of Psychotria bacteriophila. J. Bacteriol. 88:776-781. 1964.-The leaf-nodule endophyte of Psychotria bacteriophila has been repeatedly isolated in pure culture from germinating seedlings and young leaves on a nitrogen-free mineral agar. Its morphological, serological, and cultural characteristics place it within the Klebsiella-Aerobacter group. The endophyte has been provisionally named Klebsiella rubiacearum. Pure cultures fix N(2) under anaerobic conditions with good efficiency (4.54 mug of N fixed/mg of glucose utilized in 3 days). Nitrogen fixation by pure cultures is intimately related to pyruvate and hydrogen metabolism.