Triterpenoidal saponins from Hydrocotyle sibthorpioides

A symbiotic bacterium of Antarctic fish reveals environmental adaptability mechanisms and biosynthetic potential towards antibacterial and cytotoxic activities

Antarctic microbes are important agents for evolutionary adaptation and natural resource of bioactive compounds, harboring the particular metabolic pathways to biosynthesize natural products. However, not much is known on symbiotic microbiomes of fish in the Antarctic zone. In the present study, the culture method and whole-genome sequencing were performed. Natural product analyses were carried out to determine the biosynthetic potential. We report the isolation and identification of a symbiotic bacterium Serratia myotis L7-1, that is highly adaptive and resides within Antarctic fish, Trematomus bernacchii. As revealed by genomic analyses, Antarctic strain S. myotis L7-1 possesses carbohydrate-active enzymes (CAZymes), biosynthetic gene clusters (BGCs), stress response genes, antibiotic resistant genes (ARGs), and a complete type IV secretion system which could facilitate competition and colonization in the extreme Antarctic environment. The identification of microbiome gene clusters indicates the biosynthetic potential of bioactive compounds. Based on bioactivity-guided fractionation, serranticin was purified and identified as the bioactive compound, showing significant antibacterial and antitumor activity. The serranticin gene cluster was identified and located on the chrome. Furthermore, the multidrug resistance and strong bacterial antagonism contribute competitive advantages in ecological niches. Our results highlight the existence of a symbiotic bacterium in Antarctic fish largely represented by bioactive natural products and the adaptability to survive in the fish living in Antarctic oceans.

Ethnomedicinal Use, Phytochemistry, and Other Potential Application of Aquatic and Semiaquatic Medicinal Plants

Medicinal plants have been treating various ailments and diseases since ancient times. Aquatic and semiaquatic medicinal plants play an essential role in human welfare to fulfill their daily needs. They have shown biological, pharmacological, nutraceutical, and commercial applications. This review aims to collect and update all recent information on ethnomedicinal, phytochemistry, pharmacological activities, and nanoparticle synthesis and their uses in aquatic and semiaquatic medicinal plants. Original research papers, review papers, short communications, and book chapters on aquatic and semiaquatic plants have been retrieved from PubMed, Web of Science, Scopus, and Google Scholar. Keywords, ethnomedicinal studies, phytochemistry, pharmacological activities, and nanoparticle synthesis from aquatic and semiaquatic medicinal plants are used for the search. Different aquatic and semiaquatic medicinal plants belonging to the families Acanthaceae, Alismataceae, Amaranthaceae, Apiaceae, Araceae, Asteraceae, Boraginaceae, Ceratophyllaceae, Cyperaceae, Fabaceae, Hydrocharitaceae, Lythraceae, Marsileaceae, Menyanthaceae, Nelumbonaceae, Nymphaeaceae, Onagraceae, Plantaginaceae, Poaceae, Polygonaceae, Pontederiaceae, Primulaceae, Scrophulariaceae, and Zingiberaceae have been studied. They are rich in alkaloids, flavonoids, terpenoids, phenolics, saponins, tannins, dietary fiber, glycosidic derivatives, carbohydrates, and proteins. These phytochemicals have been used for their antimicrobial, antioxidant, hepatoprotective, sedative, anticonvulsant, cytotoxic, antiparasitic, and antidiabetic activities. Besides this, various parts of the plants are used as dietary supplements and green nanoparticle synthesis. These plants are also known for their commercial value and are used as an ingredient in some pharmaceutical industries.

Antiproliferative activity of new pentacyclic triterpene and a saponin from Gladiolus segetum Ker-Gawl corms supported by molecular docking study

A new triterpenoidal saponin identified as 3-O-[β-d-glucopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 4)-β-d-xylopyranosyl]-2β,3β,16α-trihydroxyolean-12-en-23,28-dioic acid-28-O-α-l-rhamnopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 2)-α-l-arabinopyranoside 1 together with a new oleanane triterpene identified as 2β,3β,13α,22α-tetrahydroxy olean-23,28-dioic acid 2 and 6 known compounds (3–8) have been isolated from Gladiolus segetum Ker-Gawl corms. The structural elucidation of the isolated compounds was confirmed using different chemical and spectroscopic methods, including 1D and 2D NMR experiments as well as HR-ESI-MS. Moreover, the in vitro cytotoxic activity of the fractions and that of the isolated compounds 1–8 were investigated against five human cancer cell lines (PC-3, A-549, HePG-2, MCF-7 and HCT-116) using doxorubicin as a reference drug. The results showed that the saponin fraction exhibited potent in vitro cytotoxic activity against the five human cancer cell lines, whereas the maximum activity was exhibited against the PC-3 and A-549 cell lines with the IC₅₀ values of 1.13 and 1.98 μg mL⁻¹, respectively. In addition, compound 1 exhibited potent activity against A-549 and PC-3 with the IC₅₀ values of 2.41 μg mL⁻¹ and 3.45 μg mL⁻¹, respectively. Interestingly, compound 2 showed the maximum activity against PC-3 with an IC₅₀ of 2.01 μg mL⁻¹. These biological results were in harmony with that of the molecular modeling study, which showed that the cytotoxic activity of compound 2 might occur through the inhibition of the HER-2 enzyme.

A new triterpenoidal saponin 1, a new oleanane triterpene 2, and 6 known compounds (3–8) have been isolated from Gladiolus segetum Ker-Gawl corms.

Acute oral toxicity evaluation of extracts of Hydrocotyle sibthorpioides in wister albino rats as per OECD 425 TG

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Toxicity was studied for Hydrocotyle sibthorpioides.

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LD₅₀ was found to be greater than 2000 mg/kg of body weight.

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Petroleum ether extract showed increase in somatomotor activity for short time.

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Methanolic and aqueous extract exhibited some change in Haematological parameters.

Hydrocotyle sibthorpioides (Family: Apiaceae) is a medicinal plant and is been a part of traditional cuisine. Hence, an acute toxicity study was performed to confirm its safety profile. Female rats (n=5) were randomly divided into 5 groups. One group served as the control and the other groups were been administered with the petroleum ether, chloroform, methanolic and aqueous extract of Hydrocotyle sibthorpioides at 2000 mg/kg body weight. Blood was collected at certain intervals to measure the haematological and biochemical parameters. The vital organs were isolated and preserved for histopathological examinations.

The result suggested that the LD₅₀ of all the extracts are greater than 2000 mg/kg body weight. There was no significant change in body weight, Behaviour, Renal Function test, Liver function test and Lipid profile. In haematological evaluation, there was an increase in RBC count and haemoglobin production post administration of methanolic and aqueous extract. The study suggested that the LD₅₀ of the plant is greater than 2000 mg/kg body weight of rats in all the extracts.

The Effect of Hydrocotyle sibthorpioides Lam. Extracts on In Vitro Dengue Replication

Objective. To investigate the potential effect of Hydrocotyle sibthorpioides Lam. (H. sibthorpioides) extracts against in vitro dengue viral replication. Methods. The cytotoxicity of H. sibthorpioides was evaluated using a cell viability assay. Cells were pre- and posttreated with water and methanol extracts of H. sibthorpioides, and the viral inhibitory effect was investigated by observing the morphological changes, which were further confirmed by plaque assay. Results. The methanolic extract cytotoxicity was higher in Vero and C6/36 cells than the cytotoxicity of the water extract. Preincubation of the cells with H. sibthorpioides extract showed nonexistent to mild prophylactic effects. The posttreatment of Vero cells with H. sibthorpioides methanolic extract presented higher antidengue activities when compared with the water extract. Surprisingly, posttreatment of C6/36 cells resulted in an enhancement of viral replication. Conclusion. H. sibthorpioides had variable effects on dengue viral replication, depending on the treatment, cell lines, and solvent types. This study provides important novel insights on the phytomedicinal properties of H. sibthorpioides extracts on dengue virus.

Screening of microorganisms from deep-sea mud for Antarctic krill (Euphausia superba) fermentation and evaluation of the bioactive compounds

Twelve kinds of strains were isolated from deep-sea mud which can use Antarctic krill powder as the sole carbon/nitrogen source. These strains were identified by 16s rDNA sequence analysis and grouped into eight different genera, including Bacillus, Shewanella, Psychrobacter, Klebsiella, Macrococcus, Aeromonas, Acinetobacter, and Saccharomyces. After fermentation of Antarctic krill powder using these strains, bioactive compounds including total phenolics, free amino acids, and enzyme activities were investigated. Meanwhile, antioxidant activities of the fermentation liquors were also detected. Results showed that bioactive compounds could be effectively produced through fermentation process by these strains, of which three strains (Bacillus subtilis OKF04, Macrococcus caseolyticus OKF09, and Aeromonas veronii OKF10) could produce more than 650 mg/L total phenolics or 2000 mg/L total free amino acids. In terms of enzyme activities, almost all of the strains showed protease activity and amylase activity, but only Bacillus cereus OKF01 and Bacillus megaterium OKF05 performed lipase activity and chitinase activity, respectively. All of the fermentation liquors showed antioxidant activity, within which Bacillus megaterium OKF05, Macrococcus caseolyticus OKF09, and Aeromonas veronii OKF10 displayed it more prominently. These results demonstrate that the Antarctic krill powder could be effectively converted by microorganisms isolated from deep-sea mud for production of bioactive compounds mixture.

Hypoxia affects cellular responses to plant extracts

ETHNOPHARMACOLOGICAL RELEVANCE

Microenvironmental conditions contribute towards varying cellular responses to plant extract treatments. Hypoxic cancer cells are known to be resistant to radio- and chemo-therapy. New therapeutic strategies specifically targeting these cells are needed. Plant extracts used in Traditional Chinese Medicine (TCM) can offer promising candidates. Despite their widespread usage, information on their effects in hypoxic conditions is still lacking. In this study, we examined the cytotoxicity of a series of known TCM plant extracts under normoxic versus hypoxic conditions.

MATERIALS AND METHODS

Pereskia grandifolia, Orthosiphon aristatus, Melastoma malabathricum, Carica papaya, Strobilanthes crispus, Gynura procumbens, Hydrocotyle sibthorpioides, Pereskia bleo and Clinacanthus nutans leaves were dried, blended into powder form, extracted in methanol and evaporated to produce crude extracts. Human Saos-2 osteosarcoma cells were treated with various concentrations of the plant extracts under normoxia or hypoxia (0.5% oxygen). 24h after treatment, an MTT assay was performed and the IC(50) values were calculated. Effect of the extracts on hypoxia inducible factor (HIF) activity was evaluated using a hypoxia-driven firefly luciferase reporter assay.

RESULTS

The relative cytotoxicity of each plant extract on Saos-2 cells was different in hypoxic versus normoxic conditions. Hypoxia increased the IC(50) values for Pereskia grandifola and Orthosiphon aristatus extracts, but decreased the IC(50) values for Melastoma malabathricum and Carica papaya extracts. Extracts of Strobilanthes crispus, Gynura procumbens, Hydrocotyle sibthorpioides had equivalent cytotoxic effects under both conditions. Pereskia bleo and Clinacanthus nutans extracts were not toxic to cells within the concentration ranges tested. The most interesting result was noted for the Carica papaya extract, where its IC(50) in hypoxia was reduced by 3-fold when compared to the normoxic condition. This reduction was found to be associated with HIF inhibition.

CONCLUSION

Hypoxia variably alters the cytotoxic effects of TCM plant extracts on cancer cells. Carica papaya showed enhanced cytotoxic effect on hypoxic cancer cells by inhibiting HIF activities. These findings provide a plausible approach to killing hypoxic cancer cells in solid tumors.

A novel compound with antioxidant activity produced by Serratia ureilytica TKU013

The secondary metabolites from the cultured supernatant of Serratia ureilytica TKU013 with squid pen as the sole carbon/nitrogen source were isolated and ascertained the mechanism of biological activity. The EtOAc layer, which has high DPPH scavenging activity, was applied to silica gel column chromatography with a gradient of CH(2)Cl(2)/MeOH solvent system, to yield A-H and MeOH fractions. The DPPH scavenging activity and cytotoxic activities against Doay and HEp-2 cell lines of these fractions were examined. The active fractions were further applied to purification by RP-HPLC, to obtain seven compounds, including a novel compound, serlyticin-A (1), together with six known compounds, serranticin (2), serratamolide A (3), thymine (4), (4-hydroxyphenyl)acetic acid (5), methyl p-hydroxybenzoate (6), and uracil (7). Their structures were determined by physical and extensive spectral analyses such as 1D and 2D NMR data, as well as comparison with literature values. Furthermore, the major secondary metabolites of EtOAc extract of the cultured supernatant were examined by the fingerprinting data of the HPLC system.

Triterpene saponins from Antonia ovata leaves

Six pentacyclic triterpenoid saponins, named antoniosides E-J along with two known alkaloids, were isolated from the leaves of Antonia ovata. Their structures were determined by the extensive use of 1D and 2D-NMR experiments along with HRESIMS analysis and acid hydrolysis. All isolated saponins contained the same pentasaccharide chain: 3-O-[β-D-glucopyranosyl-(1→2)]-[β-D-glucopyranosyl-(1→4)]-[β-D-glucopyranosyl-(1→3)-α-L-arabinopyranosyl(1→6)]-β-D-glucopyranoside, linked at C-3 of esterified derivatives of polyhydroxyoleanene triterpenoids (theasapogenol A and 15α-hydroxy-theasapogenol A). Isolated compounds were evaluated for their cytotoxic activity against KB cell line by a WST-1 assay, and the IC(50) values ranged from 3.3 to 5.3 μM.

Discrimination of three Pegaga (Centella) varieties and determination of growth-lighting effects on metabolites content based on the chemometry of 1H nuclear magnetic resonance spectroscopy

The metabolites of three species of Apiaceae, also known as Pegaga, were analyzed utilizing (1)H NMR spectroscopy and multivariate data analysis. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) resolved the species, Centella asiatica, Hydrocotyle bonariensis, and Hydrocotyle sibthorpioides, into three clusters. The saponins, asiaticoside and madecassoside, along with chlorogenic acids were the metabolites that contributed most to the separation. Furthermore, the effects of growth-lighting condition to metabolite contents were also investigated. The extracts of C. asiatica grown in full-day light exposure exhibited a stronger radical scavenging activity and contained more triterpenes (asiaticoside and madecassoside), flavonoids, and chlorogenic acids as compared to plants grown in 50% shade. This study established the potential of using a combination of (1)H NMR spectroscopy and multivariate data analyses in differentiating three closely related species and the effects of growth lighting, based on their metabolite contents and identification of the markers contributing to their differences.

Triterpenoid saponins from Hydrocotyle bonariensis Lam

Phytochemical investigation of the under-ground parts of Hydrocotyle bonariensis led to the isolation of five oleanane-type triterpenoid saponins, 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-21-O-(2-methylbutyroyl)-22-O-acetyl-R(1)-barrigenol, 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-21-O-(2-methylbutyroyl)-28-O-acetyl-R(1)-barrigenol, 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-21-O-acetyl-R(1)-barrigenol, 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-R(1)-barrigenol, and 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-22-O-(2-methylbutyroyl)-A(1)-barrigenol, together with the known saniculoside-R1. Their structures were established by 2D NMR techniques and mass spectrometry. Six compounds were evaluated against two human colon cancer cell lines, HCT 116 and HT-29. Two compounds showed weak cytotoxicity with IC(50) 24.1 and 24.0, 83.0 and 83.6 μM against HT-29 and HCT 116, respectively.

Isolation and identification of a novel antioxidant with antitumour activity from Serratia ureilytica using squid pen as fermentation substrate

The antioxidant activity of the culture supernatant of Serratia ureilytica TKU013 with squid pen as the sole carbon/nitrogen source was assessed by three methods, and the phenolic contents were assayed. The supernatant with the highest antioxidant activity was further purified by liquid-liquid partition, revealing the ethyl acetate extract exhibited the strongest antioxidant activity and the highest total phenolic content. Eight fractions were retrieved from silica gel column chromatography of this extract, designated F1-F8. F4 was found to possess the strong antioxidative activity and the highest total phenolic content and also exhibited strong cytotoxic activities against two different tumoural cell lines. A new compound (Serranticin) with antioxidant and antitumor activity was obtained from F4. The structure of Serranticin is analogous to that of siderophores (hexacoordinated catecholamine), which are iron chelators. As such, Serranticin has the potential for use as a deferration agent in various iron overload diseases.

Saponins as cytotoxic agents: a review

Saponins are natural glycosides which possess a wide range of pharmacological properties including cytotoxic activity. In this review, the recent studies (2005-2009) concerning the cytotoxic activity of saponins have been summarized. The correlations between the structure and the cytotoxicity of both steroid and triterpenoid saponins have been described as well as the most common mechanisms of action.

Triterpenoids

This review covers the isolation and structure determination of triterpenoids including squalene derivatives, protostanes, lanostanes, holostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, lupanes, oleananes, friedelanes, ursanes, hopanes, isomalabaricanes and saponins; 574 references are cited.

Triterpenoids and flavonoids from celery (Apium graveolens)

Three new triterpenoids, 11,21-dioxo-2beta,3beta,15alpha-trihydroxyurs-12-ene-2-O-beta-D-glucopyranoside (1), 11,21-dioxo-3beta,15alpha,24-trihydroxyurs-12-ene-24-O-beta-D-glucopyranoside (2), and 11,21-dioxo-3beta,15alpha,24-trihydroxyolean-12-ene-24-O-beta-D-glucopyranoside (3), and two new flavonoids, apigenin-7-O-[2''-O-(5'''-O-feruloyl)-beta-D-apiofuranosyl]-beta-D-glucopyranoside (4) and chrysoeriol-7-O-[2''-O-(5'''-O-feruloyl)-beta-D-apiofuranosyl]-beta-d-glucopyranoside (5), were isolated from the whole plant of fresh celery (Apium graveolens), together with 10 known flavonoids. The structures of the new compounds were elucidated by analysis of spectroscopic data. The inhibitory effects of the compounds isolated on nitric oxide production in lipopolysaccaride-activated macrophages were evaluated.

New triterpene saponins from Duranta repens Linn. and their cytotoxic activity

From the leaves of Duranta repens (Verbenaceae) two new triterpene saponins, named durantanin IV (1) and V (2) were isolated. In addition, ten known compounds were isolated, namely a bidesmosidic saponin, oleanolic acid, three phenylethanoids and five flavonoids. All metabolites were isolated for the first time from this genus except for 3 (oleanolic acid) and 7 (E/Z acteoside). The structures were determined mainly by spectroscopic methods (UV, IR, HRESI-MS, ¹H-, ¹³C-NMR, ¹H-¹H COSY, HSQC and HMBC). Cytotoxic screening of the chloroform, ethyl acetate and methanol extracts was carried out on brine shrimps. In addition, the investigated methanol extract and compounds 1, 2 and 7 showed significant cytotoxic activity against a HepG2 cell line.