Anti-HIV diphyllin glycosides from Justicia gendarussa
Graphical abstract
Two new anti-HIV arylnaphthalide lignan glycosides were isolated from the stems and barks of Justicia gendarussa. Justiprocumin B (2) displayed potent inhibition activity against a broad spectrum of HIV-1 strains including the NRTI and NNRTI resistant strains.
Introduction
The pandemic AIDS (acquired immunodeficiency syndrome) disease has killed more than 36 million people, and the number of the HIV infected patients exceeds 39 million (UNAIDS, 2016a, UNAIDS, 2016b, WHO, 2016a) since its first report in 1981 in the United States (CDC, 1981, Barré-Sinoussi et al., 1983). AIDS is presently the leading cause of death in Africa and ranked as the six leading cause of death worldwide (WHO, 2016b). The efficacy of the drugs available to treat HIV/AIDS patients on the market is diminishing due to drug resistance and side effects. Further, there is no effective vaccine currently available against HIV. Development of new anti-HIV therapeutics is thus urgently needed.
Higher plants have been used for the treatment of human diseases for thousands of years, and over 130 plant-derived chemicals are important drugs currently in clinical use around the World (Tsang et al., 2007, Taylor, 2005). Plant natural products have been an important source for discovery of anti-HIV agents. For example, calanolide A, a non-nucleoside reverse transcriptase inhibitor (NNRTI), was first isolated from a Malaysian plant Callophylum lanigerum (Kashman et al., 1992). It has been investigated continuously in clinical trials (ClinicalTrials.gov, 2016a). Betulinic acid is a triterpene, which can be found in many plant species. One of its derivatives (PA457) had been in Phase II clinical study for the treatment of HIV (ClinicalTrials.gov, 2016b). Ingenol is a diterpenoid isolated from the dried roots of Euphorbia desmondi (Evans and Kinghorn, 1974). Its triacetate showed potent anti-HIV activity (Fujiwara et al., 1996a, Fujiwara et al., 1996b). Conocurvone, a trimeric naphthoquinone isolated from an Australian plant Conospermum incurvum Lindley (Decosterd et al., 1993), is under drug development by an Australian company. Its anti-HIV mechanism of action occurs in the late phase of the viral replication cycle.
In the past 15 years, our medicinal plant research program has evaluated antiviral activity of more than 4500 tropical plants, and discovered more than 50 active plant leads against HIV, HCV and avian flu virus (H5N1) (Guan et al., 2016, Hoang et al., 2002, Li et al., 2015, Pan et al., 2014, Rumschlag-Booms et al., 2011, Soejarto et al., 2006, Song et al., 2016, Zhang et al., 2001, Zhang et al., 2003a, Zhang et al., 2003b, Zhang et al., 2003c, Zhang et al., 2004, Zhang et al., 2005, Zhang et al., 2009). Among the active plant leads, a CH2Cl2 extract (SV5614) made from the stems and roots of Justicia gendarussa (Acanthaceae) showed complete inhibition against HIV replication at a concentration 20 μg/mL. The anti-HIV activity of this plant was further confirmed by evaluation of the MeOH extract (SVA5614) made from the subsequently recollected stem and bark materials of the plant species in the same area, which showed that SVA5614 was able to inhibit HIV replication at a low concentration (IC50 0.04 μg/mL) without cytotoxicity when tested at much higher concentration of 20 μg/mL.
J. gendarussa is a medicinal plant that has been used for the treatment of various diseases in Asian countries. The plant is a bush of up to about 1.5 m in height, and is found in Southern Asia including China, Vietnam, Thailand, India, Sri Lanka, Pakistan and Indonesia. The whole plant has been used as a native medicinal plant for the treatment of injury from falls and rheumatism in the provinces of China including Guangdong, Guangxi and Taiwan (Jiangsu, 1986). The plant is also widely distributed in the other Southern Asia countries, and is being used in these countries for the treatment of fever, hemiplegia, arthritis, headache, respiratory disorders, muscle pain and digestive trouble (Kavitha et al., 2014, Paval et al., 2009). Bioassay-guided fractionation of the plant extract SVA5614 led to the isolation of two anti-HIV compounds. The compounds, designated as justiprocumins A (1) and B (2) respectively, belong to arylnaphthalide lignan (ANL) glycosides, which are determined to be novel molecules (Fig. 1). In addition, we have analyzed the active and non-active fractions of the plant extract using HPLC techniques, and discovered that only the active fractions contained ANL glycosides. The inactive fractions are devoid of these molecules.
The current paper reports the isolation, identification and biological evaluation of the anti-HIV ANL glycoside from the plant J. gendarussa.
Section snippets
Results and discussion
The dried, milled plant material (4.0 kg) was extracted with MeOH to afford a MeOH extract (SVA5614, 155 g). Chromatographic fractionation of SVA5614 over a silica gel column afforded the active fraction F26, which was subjected to preparative HPLC separation to yield 8 fractions (F41–F48). The active fractions F45 and F48 were found to consist of pure compounds, which were given the names of justiprocumins A (1) and B (2), respectively. The two new compounds were elucidated to belong to
Conclusion
Two new anti-HIV lead compounds [justiprocumins A (1) and B (2)] were successfully isolated from the stems and the barks of J. gendarussa using our “One-Stone-Two-Birds” bioassay evaluation guided system. The cell-based evaluation protocol was using the viral entry mediated glycoprotein (GP) incorporated onto another virus to produce so-called pseudovirion particles, which retained the viral entry property but with alleviated safety concerns (Li et al., 2015, Rumschlag-Booms et al., 2011). The
General experimental procedures
Optical rotations were measured with a Perkin-Elmer model 241 polarimeter. IR spectra were recorded on a Jasco FT/IR-410 spectrometer, equipped with a Specac Silver Gate ATR system by applying a film on a Germanium plate (Jasco, Maryland). 1D and 2D NMR spectra were recorded on a Bruker DRX-500 MHz or a Bruker DPX-400 MHz or a Bruker DPX-360 MHz spectrometer (Germany). Chemical shifts (δ) were expressed in ppm with reference to the solvent signals (methanol-d4 CD3OD: 1H: 3.30 ppm, 13C:
Acknowledgements
This project was supported by the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. HKBU 262912), the Health and Medical Research Fund (12132161) of the Food and Health Bureau, Hong Kong SAR, Faculty Research Grants, Hong Kong Baptist University (FRG2/11-12/134 and FRG2/14-15/047), NIH Grants 3U01TW001015-10S1 and 2U01TW001015-11A1, administered by the Fogarty International Center as part of an International Cooperative Biodiversity Groups (ICBG)
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These authors contributed equally to this work.
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Present address: Northeastern Illinois University, 5500 N St Louis Ave, Chicago, Illinois 60625, USA.