Anti-AIDS agents, 21. Triterpenoid saponins as anti-HIV principles from fruits of Gleditsia japonica and Gymnocladus chinensis, and a structure-activity correlation

Comprehensive profiling of chemical composition of Gleditsiae spina using ultra-high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry

RATIONALE

Gleditsiae spina (GS) is an important herb used in traditional and folk medicinal systems of East Asian countries for its various medicinal properties. In China, it has been traditionally used through the centuries for its anticancer, detoxication, detumescence, apocenosis, and antiparasitic effects. Although some of its ingredients have been isolated and identified, most active constituents remain unknown. Past research mostly exploited nuclear magnetic resonance for the identification of compounds, which is suitable for monomers only. Moreover, the extraction and isolation procedures for obtaining purified molecules are time consuming. Therefore, establishing an efficient approach will assist in rapid discovery of the potential active ingredients of GS. The present study aimed to identify the chemical constituents in GS by a data analysis strategy using ultra-high-performance liquid chromatography combined with quadrupole time-of-flight tandem mass spectrometry.

METHODS

First, the theoretical formula of the candidate compound was calculated using the accurate mass of the precursor/adduct ions. Second, the compounds were classified by the diagnostic ions from the MS/MS data. Third, characteristic ion filtering was used to identify the structures. Finally, the diverse skeletons and substitutions were further identified through the neutral loss in the GS.

RESULTS

A total of 277 compounds were identified in GS, comprising 169 flavonoids, 70 lignans, and 38 other compounds. At least 43 potential new compounds were represented.

CONCLUSIONS

This experiment devised an efficient and systematic method for detecting complex compounds and provided a foundation for future research into bioactive ingredients and quality control of GS.

Molluscicidal Activity of Compounds From the Roots of Aralia armata Against the Golden Apple Snail (Pomacea canaliculata)

Background: Aralia armata (Araliaceae) is considered to exhibit effective molluscicidal activity, however, the relationship between the chemical components and molluscicidal activity has not been clearly elucidated. This research attempts to decipher these correlations among the 15 compounds isolated from Vietnam-grown A. armata roots against the freshwater snail, Pomacea canaliculata, a gastropod causing severe damage in agricultural production. Methods: Fifteen saponins were isolated from the methanol root extract of A. armata using chromatographic methods and were identified using spectroscopic techniques. The compounds were screened for molluscicidal activity against P. canaliculata, as well as toxicity against brine shrimp ( Artemia sp.) and phytotoxicity against rice germination and growth. Results: The saponin compounds exhibited extraordinary inhibition of P. canaliculata with LC50 values ranging from 7.90 to 17.50 µg/mL. Notably, the active compounds from A. armata exhibit safety for both nontarget aquatic animals, specifically Artemia sp. with LC50 values between 148.55 and 193.22 µg/mL, and the growth and development of Oryza sativa L. plants showed very little difference compared with the negative control . A molecular docking analysis indicated P. canaliculata acetylcholinesterase (PcAChE) and the actin-binding protein villin (PcVillin) to be potential biomolecular targets of the A. armata saponins. Conclusion: The present experimental and in silico data illustrate the potential of A. armata in agricultural applications.

Anti-HIV and Anti-Candidal Effects of Methanolic Extract from Heteropterys brachiata

Nowadays, the HIV pandemic is far from controlled. HIV+/AIDS patients show a serious risk of developing resistance to HIV antiretroviral drugs and to be orally colonized by albicans and non-albicans Candida strains resistant to antifungals. As a consequence, new drugs that possess anti-candidal and anti-HIV effects would represent an alternative in the comprehensive treatment of HIV+/AIDS patients. The present study evaluates the possible anti-HIV and anti-Candida effects of a methanolic extract from Heteropterys brachiata (Hb MeOH), an American tropical plant. The anti-HIV effect of Hb MeOH was tested using a non-radioactive colorimetric method (Lenti RT^® Activity Assay; Cavidi Tech) that uses reverse transcriptase of HIV-1 enzyme as enzymatic target. The anti-candidal effect of HbMeOH extract was evaluated by following a standardized test protocol of microdilution for yeast using the Candida albicans strain ATCC^® 90028. The Hb MeOH at 1 mg/mL concentration shows 38.5% RT-HIV inhibition, while Hb MeOH at 10 mg/mL concentration produced 98% C. albicans growth inhibition. Our findings show that the Hb MeOH possesses a strong anti-candidal activity and moderate anti-HIV effect and suggests that the plant extract could be considered as a potential candidate for HIV/AIDS treatment.

Natural Products with Inhibitory Activity against Human Immunodeficiency Virus Type 1

Infections caused by human immunodeficiency virus (HIV) are considered one of the main public health problems worldwide. Antiretroviral therapy (ART) is the current modality of treatment for HIV-1 infection. It comprises the combined use of several drugs and can decrease the viral load and increase the CD4⁺ T cell count in patients with HIV-1 infection, thereby proving to be an effective modality. This therapy significantly decreases the rate of morbidity and mortality owing to acquired immunodeficiency syndrome (AIDS) and prolongs and improves the quality of life of infected patients. However, nonadherence to ART may increase viral resistance to antiretroviral drugs and transmission of drug-resistant strains of HIV. Therefore, it is necessary to continue research for compounds with anti-HIV-1 activity, exhibiting a potential for the development of an alternative or complementary therapy to ART with low cost and fewer side effects. Natural products and their derivatives represent an excellent option owing to their therapeutic potential against HIV. Currently, the derivatives of natural products available as anti-HIV-1 agents include zidovudine, an arabinonucleoside derivative of the Caribbean marine sponge (Tectitethya crypta), which inhibits the reverse transcriptase of the virus. This was the first antiviral agent approved for treatment of HIV infection. Additionally, bevirimat (isolated from Syzygium claviflorum) and calanolide A (isolated from Calophyllum sp.) are inhibitors of viral maturation and reverse transcription process, respectively. In the present review, we aimed to describe the wide repertoire of natural compounds exhibiting anti-HIV-1 activity that can be considered for designing new therapeutic strategies to curb the HIV pandemic.

Emerging paradigms of viral diseases and paramount role of natural resources as antiviral agents

In the current scenario, the increasing prevalence of diverse microbial infections as well as emergence and re-emergence of viral epidemics with high morbidity and mortality rates are major public health threat. Despite the persistent production of antiviral drugs and vaccines in the global market, viruses still remain as one of the leading causes of deadly human diseases. Effective control of viral diseases, particularly Zika virus disease, Nipah virus disease, Severe acute respiratory syndrome, Coronavirus disease, Herpes simplex virus infection, Acquired immunodeficiency syndrome, and Ebola virus disease remain promising goal amidst the mutating viral strains. Current trends in the development of antiviral drugs focus solely on testing novel drugs or repurposing drugs against potential targets of the viruses. Compared to synthetic drugs, medicines from natural resources offer less side-effect to humans and are often cost-effective in the productivity approaches. This review intends not only to emphasize on the major viral disease outbreaks in the past few decades and but also explores the potentialities of natural substances as antiviral traits to combat viral pathogens. Here, we spotlighted a comprehensive overview of antiviral components present in varied natural sources, including plants, fungi, and microorganisms in order to identify potent antiviral agents for developing alternative therapy in future.

Medicinal Plants Used in the Treatment of Human Immunodeficiency Virus

Since the beginning of the epidemic, human immunodeficiency virus (HIV) has infected around 70 million people worldwide, most of whom reside is sub-Saharan Africa. There have been very promising developments in the treatment of HIV with anti-retroviral drug cocktails. However, drug resistance to anti-HIV drugs is emerging, and many people infected with HIV have adverse reactions or do not have ready access to currently available HIV chemotherapies. Thus, there is a need to discover new anti-HIV agents to supplement our current arsenal of anti-HIV drugs and to provide therapeutic options for populations with limited resources or access to currently efficacious chemotherapies. Plant-derived natural products continue to serve as a reservoir for the discovery of new medicines, including anti-HIV agents. This review presents a survey of plants that have shown anti-HIV activity, both in vitro and in vivo.

Tubeimoside-1, Triterpenoid Saponin, as a Potential Natural Cancer Killer

Nature, an expert craftsman of molecules, has generated extensive array of bioactive molecular entities. It persists as an inexhaustible resource for discovery of drugs and supplied enormous scaffold diversification for development into effectual drugs to treat multiple pathological conditions. This review provides an update on the sources, biological, and pharmacological effects of nature's gift, a triterpenoid saponin, tubeimoside-1 which is a major bioactive constituent of the bulb of Bolbostemma paniculatum. Tubeimoside-1 is known to possess various pharmacological properties such as anti-cancer, anti-HIV, and anti-inflammatory. Recently, anti-proliferative potential of tubeimoside-1 has been widely studied. The present review article seeks to cover the recent developments of tubeimoside-1′s pharmacological position in the arena of herbal drugs, providing an insight into its current status in therapeutic pursuits. This anti-cancer triterpenoid saponin fight cancer progression by induction of apoptosis, cell cycle arrest, and inhibiting metastasis by specifically targeting multiple signaling pathways those are usually deregulated in various cancers. The reported data recommend tubeimoside-1′s mutitarget activity in preference to single effect that may perform an imperative role towards developing tubeimoside-1 into potential pharmacological drug.

Gleditsia species: An ethnomedical, phytochemical and pharmacological review

ETHNOPHARMACOLOGICAL RELEVANCE

The plants in the genus Gleditsia, mainly distributed in central and Southeast Asia and North and South America, have been used as local and traditional medicines in many regions, especially in China, for the treatment of measles, indigestion, whooping, smallpox, arthrolithiasis, constipation, diarrhea, hematochezia, dysentery, carbuncle, etc. This present paper systemically reviews the miscellaneous information surrounding its traditional use, phytochemistry and pharmacology to provide opportunities and recommendations for the future research.

MATERIALS AND METHODS

The scientific literatures were systematically searched from scientific databases (PubMed, Scopus, Elsevier, SpringerLink, SciFinder, Google Scholar and others). In addition, the ethnopharmacological information on this genus was mainly acquired from Chinese and Korean herbal classics, and library catalogs.

RESULTS

More than 60 compounds including triterpenes, sterols, flavonoids, alkaloids, phenolics and their derivatives were isolated from Gleditsia japonica Miq., Gleditsia sinensis Lam., Gleditsia caspica Desf. and Gleditsia triacanthos L. Among these compounds, triterpenoid saponins were the main constituents of Gleditsia species. Moreover, the crude extracts and purified molecules were tested, revealing diverse biological activities such as anti-tumor, anti-inflammatory, anti-allergic, anti-hyperlipidemic, analgesic, antimutagenic, antioxidant, anti-HIV, antibacterial, antifungal activities, etc. Among these biological studies, the possible mechanisms of antitumor action are stressed in this review, and these include causing cytotoxicity to cancer cells, inhibition of proliferation of cancer cells by affecting their growth, regeneration and apoptosis, inhibition of basic fibroblast growth factor (bFGF) and nitric oxide (NO), modulation of the oncogenic expression and telomerase activity results, inhibition of the expression of pro-angiogenic proteins, as well as down-regulation of intra/extracellular proangiogenic modulators, etc.

CONCLUSIONS

On the basis of preliminary research on Gleditsia genus it could be stated that saponins investigations may be more promising in future. Although 32 compounds of 67 identified compounds were saponins, modern pharmacological research on saponins were not a priority in Gleditsia species. Therefore, more bioactive experiments and in-depth mechanisms of action are required for elucidating their roles in physiological systems. Moreover, the present review also highlights that analgesic, anti-tumor and anti-HIV activities should have priority in saponins research. Additionally, it is imperative to explore more structure-activity relationships and possible synergistic actions of triterpenoid saponins for revaluating their pharmacological activities.

Caspicaosides E-K, triterpenoid saponins and cytotoxic acylated saponins from fruits of Gleditsia caspica Desf

Seven bisdesmosidic triterpenoid saponins named caspicaosides E-K, were isolated from the methanolic fruit extract of Gleditsia caspica Desf. Their structures were determined by 1D and 2D NMR spectroscopy as well as high resolution mass spectrometry and acid hydrolysis. The saponins comprised echinocystic acid or oleanolic acid as the aglycone and saccharide moieties at C-3 and C-28. Like most Gleditsia saponins, the oligosaccharide moiety at C-3 was identified as β-D-xylopyranosyl-(1→2)-α-L-arabinopyranosyl-(1→6)-β-D-glucopyranosyl. The common oligosaccharide moiety linked to C-28 was determined as β-D-xylopyranosyl-(1→3)-β-D-xylopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranosyl with the presence of additional β-D-galactopyranose unit and/or another α-L-rhamnopyranose moiety. The C-28 saccharide moiety was acylated with a monoterpenic acid unit or a monoterpenic acid linked to a monoterpene-arabinoside unit at the ester-β-D-glucopyranose C-6. Esterification of C-2 and C-3 hydroxyl groups of the terminal α-L-rhamnopyranose unit with a monoterpenic acid and epoxy-monoterpenic acid units, respectively, or with two identical monoterpenic acid units, was also shown. The acylated saponins caspicaosides G-K were assayed for their in vitro cytotoxicities against the three cell lines HCT116, HepG2 and MCF7. The tested saponins showed moderate to strong activities.

Synthesis and anti-cancer activity of a glycosyl library of N-acetylglucosamine-bearing oleanolic acid

N-Acetylglucosamine-bearing triterpenoid saponins (GNTS) were reported to be a unique type of saponins with potent anti-tumor activity. In order to study the structure-activity relationship of GNTS, 24 oleanolic acid saponins with (1 --> 3)-linked, (1 --> 4)-linked, (1 --> 6)-linked N-acetylglucosamine oligosaccharide residues were synthesized in a combinatorial and concise method. The cytotoxicity of these compounds toward the leukemia cell line HL-60 and the colorectal cancer cell line HT-29 could not be improved. Half maximal inhibition below 10 μM was achieved in one single case. The study revealed that the activity decreased following the order of 3' > 4' > 6' glycosyl modifications. GNTS that incorporated (D/L)-xylose and L-arabinose at positions 3' and 4' were more potent than those bearing other sugars.

Three triterpenoid saponins acylated with monoterpenic acid from Gymnocladus chinensis

A new triterpenoid saponin acylated with monoterpenic acid, together with two known triterpenoid saponins, has been isolated from the fruit of Gymnocladus chinensis Baill. Their structures were elucidated as 2β,23-dihydroxy-3-O-α-L-rhamnopyranosyl-21-O-{(6S)-2-trans-2,6-dimethyl-6-O-[3-O-(β-D-glucopyranosyl)-4-O-((6S)-2-trans-2,6-dimethyl-6-hydroxy-2,7-octadienoyl)-β-L-arabinopyranosyl]-2,7-octadienoyl}-acacic acid 28-O-β-D-xylopyranosyl-(1 → 3)-β-D-xylopyranosyl-(1 → 4)-α-L-rhamnopyranosyl-(1 → 2)-[α-L-rhamnopyranosyl-(1 → 6)]-β-D-glucopyranosyl ester (1), gymnocladus saponin E (2), and gymnocladus saponin F(2) (3).

Concise synthesis of two natural triterpenoid saponins, oleanolic acid derivatives isolated from the roots of Pulsatilla chinensis

The first synthesis of two natural triterpenoid saponins, which were isolated from the roots of Pulsatilla chinensis and exhibited excellent in vitro cytotoxic activity against HL-60 cells, was concisely achieved in a convergent approach. We employed an odourless 2-methyl-5-tert-butylphenyl (Mbp) thioglycoside and trichloroacetimidate donors in one-pot reaction as a key step.

Bioactive Complex Triterpenoid Saponins from the Leguminosae Family

Many classes of phytochemical products are finding therapeutic use, for example, complex triterpenoid saponins containing in their structures monoterpene moieties. Some of these compounds possess cytotoxic, anti-HIV and adjuvant activities. This review aims to give an overview of these complex triterpenoid saponins with biological activity from the Leguminosae.

New developments in natural products-based anti-AIDS research

This review discusses anti-HIV natural products from several compound classes, including terpenoids, coumarins, alkaloids, polyphenols, tannins, and flavonoids. Natural products can provide novel anti-AIDS chemotherapeutic leads that are structurally unique or have new mechanisms of action. The drug discovery and development process proceeds from bioactivity-directed isolation and identification of a promising lead natural product, followed by rational design-based structural modification and structure-activity relationship analyses to optimize the lead compound as a drug candidate. This process is notably exemplified by the discovery of the modified betulinic acid derivative, DSB [PA-457], which is currently in Phase II clinical trial and is the first-in-class HIV maturation inhibitor (MI).

Echinocystic acid induces apoptosis in HL-60 cells through mitochondria-mediated death pathway

Echinocystic acid (EA) is a natural triterpone enriched in various herbs and used for medicinal purpose in many Asian countries. In the present study, we reported that EA can induce apoptosis in human promyelocytic leukemia cells (HL-60), as characterized by DNA fragmentation, poly (ADP) ribose polymerase cleavage. The efficacious induction of apoptosis was observed at 100 microM for 6 h. Further molecular analysis showed that EA induced the cleavage of Bid protein, the loss of mitochondrial membrane potential (DeltaPsim) cytochrome c release from mitochondria into cytosol, and activation of caspase-3, -8 and -9. However, EA did not generate reactive oxygen species (ROS), and antioxidants including N-acetyl cysteine and catalase could not block EA-induced apoptosis in the HL-60 cells. These data suggest that EA induces apoptosis in HL-60 cells through ROS-independent mitochondrial dysfunction pathway.

Natural Products as Antiviral Agents

Since the ancient times, natural products have served as a major source of drugs. About fifty percent of today's pharmaceutical drugs are derived from natural origin. Interest in natural products as a source of new drugs is growing due to many factors that will be discussed in this article. Viruses have been resistant to therapy or prophylaxis longer than any other form of life. Currently, there are only few drugs available for the cure of viral diseases including acyclovir which is modeled on a natural product parent. In order to combat viruses which have devastating effects on humans, animals, insects, crop plants, fungi and bacteria, many research efforts have been devoted for the discovery of new antiviral natural products. Recent analysis of the number and sources of antiviral agents reported mainly in the annual reports of medicinal chemistry from 1984 to 1995 indicated that seven out of ten synthetic agents approved by FDA between 1983-1994, are modeled on a natural product parent. It has been estimated that only 5-15% of the approximately 250,000 species of higher plants have been systematically investigated for the presence of bioactive compounds while the potential of the marine environment has barely been tapped. The aim of this review is to provide an overview on the central role of natural products in the discovery and development of new antiviral drugs by displaying 340 structures of plant, marine and microbial origin that show promising in vitro antiviral activity.

Mechanism of antiviral activity of triterpenoid saponins

Triterpenoid saponins are naturally occurring sugar conjugates of triterpenes possessing various biological activities, including antiviral action. Two substances isolated from natural sources were tested against herpes simplex virus type 1 replication. They did not show evidence of cytotoxicity under antiviral test conditions. The triterpenoid saponin, isolated from a Brazilian plant (s21), represents the oleanane group and inhibited herpes simplex virus type 1 DNA synthesis. The triterpenoid saponin, isolated from a Chinese plant (s17), represents the ursane group and seemed to inhibit viral capsid protein synthesis of herpes simplex virus type 1.