Linking phytochemistry to traditional uses and pharmacology of an underexplored genus - Psydrax: a review.

The genus Psydrax is one of the ethno-medicinally important genera of the Rubiaceae family which has only received a limited scientific attention, despite coming from a pharmacologically and phytochemically important plant family. The genus has found applications in ethnomedical management of diabetes, stomach disorders, inflammations, cardiovascular diseases, epilepsy, wounds, malaria and fever. To unveil knowledge gaps, stimulate research interest and unravel opportunities for drug discovery from the genus Psydrax, we have carried out an extensive review on its traditional applications, phytochemistry and pharmacology for the first time. Literature on these topics was obtained from Google Scholar, Pubmed and ScienceDirect journal articles published from 1788 to September, 2021. Only articles written in English were reviewed. While several species of Pysdrax used in traditional medicine have not been chemically explored for drug discovery, over a hundred secondary metabolites have so far been identified in few species of the genus, and majority of these chemotaxonomic markers are iridoids. Bioactive extracts and some isolated constituents of Psydrax species have shown various in vitro and in vivo pharmacological properties including anti-hyperglycemia, anti-inflammatory, anticonvulsant and antimicrobial, and thus, support some of the ethnomedical uses of the plants. For an evidence-informed application of the genus, Psydrax, in traditional medicine, more ethnobotanical surveys, elaborate in vivo pharmacological assays, in-depth toxicity and holistic phytochemical studies are required to fully exploit more species of the genus prior to future clinical studies. Following documented traditional uses of Psydrax species, the deliberate cultivation of medicinal plants under this genus is recommended for sustainability in medicinal plant utilization.

Newboulasides A and B, two new caffeic acid glycosides from Newbouldia laevis with α-amylase inhibitory activity.

Chemical investigation of the ethanol extract of the leaves of Newbouldia laevis (P. Beauv) led to the isolation of two new caffeic acid glycosides, Newboulasides A (1) and B (2). The structures of these compounds were determined on the basis of extensive spectroscopic methods, including 1D-, 2D-NMR and MS data. The extracts and fractions and the isolated compounds were evaluated for their inhibition of α-amylase enzyme activity. The extract showed inhibition of α-amylase activity with IC50 value of 102.91 µg/mL, while the isolated compounds (1 and 2) exhibited pronounced inhibition with IC50 values of 4.95 and 4.44 µg/mL respectively, comparable to the standard - Acarbose with IC50 value of 4.05 µg/mL. Our findings demonstrated that the inhibition of α-amylase activity may be part of the mechanisms through which N. leavis exhibits antidiabetic effect.

Antiviral activity of Salidroside from the leaves of Nigerian mistletoe (Loranthus micranthus Linn) parasitic on Hevea brasiliensis against respiratory syncytial virus.

Isolated Salidroside from the leaves of Nigerian mistletoe (Loranthus micranthus Linn) parasitic on Hevea brasiliensis was evaluated for its antiviral activity against respiratory syncytial virus. Semi- preparative HPLC separation of the ethyl acetate fraction of the leave extract of Loranthus micranthus Linn parasitic on Hevea brasiliensis led to the isolation of a polyphenol. Using spectroscopic methods (1D and 2D NMR and mass spectroscopic data) as well as by comparison with literature data the structure of the compound was determined as 6-O-galloyl salidroside. The antiviral activity of the isolated compound was evaluated against the respiratory syncytial virus. The isolated Salidroside showed potent inhibition towards a recombinant straining respiratory syncytial virus with Inhibitory Concentration (IC 50) value of 10.3±1.50 µg/mL. The result indicates that Salidroside is an efficient antiviral agent against RSV infection and might be useful for the management of RSV pathogenesis.

Mosquito adulticidal activity of the leaf extracts of Spondias mombin L. against Aedes aegypti L. and isolation of active principles.

BACKGROUND & OBJECTIVES: Aedes aegypti is a domestic mosquito and one of the primary vectors for dengue and yellow fever. Since, it is a vector of deadly diseases, its control becomes essential. Medicinal plants may be an alternative to adulticidal agents since they contain rich source of bioactive compounds. This study was designed to determine the adulticidal activity of Spondias mombin leaf methanol crude extract, n-hexane, dichloromethane and ethyl acetate fractions against female adults of Ae. aegypti mosquitoes and isolate active compound(s) responsible for the bioactivity. METHODS: All leaf extract and fractions were evaluated for adulticidal activity against Ae. aegypti mosquitoes. Adult mortality was observed after 24 h of exposure. The dichloromethane fraction was further purified being the most active fraction using silica gel column chromatography and the active compounds were identified with the aid of HPLC and LC-ESI-MS/MS. The LC50 and LC90 were determined by Probit analysis. RESULTS: Dichloromethane fraction was the most effective fraction with LC50 value of 2172.815 µg/ml. Compounds identified were mainly ellagic acid and 1-O-Galloyl-6-O-luteoyl-α-D-glucose. INTERPRETATION & CONCLUSION: The S. mombin leaf extracts and fractions proved to be a strong candidate for a natural, safe and stable adulticide, alternative to synthetic adulticide.

Larvicidal activity of the leaf extracts of Spondias mombin Linn. (Anacardiaceae) from various solvents against malarial, dengue and filarial vector mosquitoes (Diptera: Culicidae).

BACKGROUND & OBJECTIVES: Aedes aegypti, Anopheles gambiae and Culex quinquefasciatus are vector mosquitoes of dengue, malaria, and filariasis, respectively. Since no vaccine is available to treat these diseases, the control of the main mosquito vectors is essential. As conventional insecticides have limited success, plants may be alternative larvicidal agents, since they contain a rich source of bioactive chemicals. The aim of this study was to evaluate the larvicidal activity of methanol crude extract, hexane, dichloromethane, acetone, ethyl acetate and methanol fractions of Spondias mombin leaf against IV instar larvae of dengue, malaria, and lymphatic filariasis vector mosquitoes. METHODS: A total of 25, IV instar larvae of each target mosquito species were exposed to various concentrations (125-1000 ppm) and were assayed in the laboratory by using the protocol of WHO 2005; the LC50 values were determined by Probit analysis. RESULTS: Hexane, dichloromethane and acetone fractions were the most effective against Ae. aegypti with LC50 values of 22.54, 42.13, 45.18 ppm, respectively. Hexane fraction registered the highest activity with LC50 of 92.20 ppm against An. gambiae. It was still hexane fraction that showed better toxicity with LC50 of 326.53 ppm against Cx. quinquefasciatus. CONCLUSION: The Spondias mombin leaf extracts proved to be a strong candidate for a natural, safe and stable mosquito larvicide to be used in population control of Ae. aegypti, An. gambiae and Cx. quinquefasciatus and so may replace the conventional Diclorvos to control malaria, dengue and filariasis in Nigeria.