Abstract
The leaf MeOH extract of Psychotria leiocarpa (Rubiaceae) showed in vitro non-cytotoxic and anti-dengue virus serotype 2 (DENV2) activity in human hepatocarcinoma cell lineage (HepG2). A one-step and cost-effective reversed-phase solid-phase extraction method based on high-performance liquid chromatography (HPLC) parameters allowed the isolation, directly from this bioactive extract, of the monoterpene indole alkaloids: N-glucopyranosyl vincosamide (1), vincosamide (2) and strictosidinic acid (3). The chemical structures were characterized based on 1D and 2D nuclear magnetic resonance (NMR), UV and high-resolution mass spectra (HRMS). The methodology has also allowed yielding a polyphenolic-rich fraction that was analyzed by high-performance liquid chromatography coupled to diode array detection and electrospray ionization tandem mass spectrometry (HPLC-DAD-ESI-MS/MS) revealing two flavonol triglycosides (4, 5) and three caffeoylquinic acid isomers (6-8). Compound 3 is reported for the first time in P. leiocarpa and all the phenolic compounds (4-8) are described for the first time in the genus Psychotria. Compounds 1-3 showed to be non-cytotoxic and anti-dengue active towards DENV2, highlighting vincosamide (2).
Highlights
Psychotria L. is the largest genus in the Rubiaceae family with near to 13000 species worldwide, mostly distributed in tropical regions.1 The phytochemical studies of the Psychotria spp. described so far have allowed identifying the genus as a source of alkaloids, terpenoids, steroids, flavonoids, tannins, cyclopeptides and phenolic compounds which may be related to the wide variety of biological activities revealed to those species, such as: cytotoxicity, analgesic, antiviral, antifungal and modulatorVol 31, No 10, 2020 a broad antioxidant activity, which was considered to be possibly associated to the species protection against oxidative stress such as wounding and UV exposure.12,14,15 Compound 2 demonstrates anti-inflammatory activity and inhibition of the enzyme acetylcholinesterase.6Dengue is a neglected disease widespread throughout the tropical and subtropical areas and its incidence has dramatically increased in the last decades.16 The World Health Organization (WHO) estimates that dengue virus (DENV) infects about 390 million people annually.16 It is being considered one of the most prevalent viral infections in the world.17,18 In Brazil, it is placed among one of the most serious public health issues.19 Currently, there is no antiviral drug approved for the routine treatment of dengue patients
We report the in vitro noncytotoxicity and anti-dengue virus serotype 2 (DENV2) effects in hepatocarcinoma cell lineage (HepG2), of the crude MeOH extract of P. leiocarpa leaves and of the monoterpene indole alkaloids N,β-D-glucopyranosyl vincosamide [1], vincosamide [2] and strictosidinic acid [3] isolated by a developed one-step reversed-phase solid-phase extraction (SPE) method based on high-performance liquid chromatography (HPLC) conditions
Quantification of DENV-2 at the conditioned medium of infected HepG2 after 48 h demonstrated a reduction of about 80% of DENV infectious particles when it was treated with the extract comparing with untreated condition (Figure 1b)
Summary
Psychotria L. is the largest genus in the Rubiaceae family with near to 13000 species worldwide, mostly distributed in tropical regions.1 The phytochemical studies of the Psychotria spp. described so far have allowed identifying the genus as a source of alkaloids, terpenoids, steroids, flavonoids, tannins, cyclopeptides and phenolic compounds which may be related to the wide variety of biological activities revealed to those species, such as: cytotoxicity, analgesic, antiviral, antifungal and modulatorVol 31, No 10, 2020 a broad antioxidant activity, which was considered to be possibly associated to the species protection against oxidative stress such as wounding and UV exposure.12,14,15 Compound 2 demonstrates anti-inflammatory activity and inhibition of the enzyme acetylcholinesterase.6Dengue is a neglected disease widespread throughout the tropical and subtropical areas and its incidence has dramatically increased in the last decades.16 The World Health Organization (WHO) estimates that dengue virus (DENV) infects about 390 million people annually.16 It is being considered one of the most prevalent viral infections in the world.17,18 In Brazil, it is placed among one of the most serious public health issues.19 Currently, there is no antiviral drug approved for the routine treatment of dengue patients. As part of our ongoing search for potential anti-dengue agents, the in vitro antiviral activities of several Brazilian Rubiaceae spp. and some of their compounds have been described.25-30 In this paper, we report the in vitro noncytotoxicity and anti-dengue virus serotype 2 (DENV2) effects in hepatocarcinoma cell lineage (HepG2), of the crude MeOH extract of P. leiocarpa leaves and of the monoterpene indole alkaloids N,β-D-glucopyranosyl vincosamide [1], vincosamide [2] and strictosidinic acid [3] isolated by a developed one-step reversed-phase SPE method based on high-performance liquid chromatography (HPLC) conditions.
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