Pregnane glycosides from Caralluma retrospiciens

Quadrangulosides A-F: new pregnane glycosides from Caralluma quadrangula

The phytochemical investigation of Caralluma quadrangula aerial parts yielded six new pregnane glycosides, quadrangulosides A-F (1-6), in addition to nine known pregnane glycosides and three known flavone glycosides. Structures of isolated phyto-constituents were elucidated via spectroscopic 1D-, 2D-NMR and spectrometric ESI-MS spectra.

Comprehensive polyoxypregnane glycosides report in Caralluma quadrangula using UPLC-ESI-Q-TOF and their antioxidant effects in human plasma

ETHNOPHARMACOLOGICAL RELEVANCE

Caralluma quadrangula (Forssk.) N.E.Br. (Syns: = Stapelia quadrangula Forssk. = Monolluma quadrangula Forssk.) is an indigenous member of the genus Caralluma and it is a rather common species on rocky hillsides in the southwestern part of Saudi Arabia. Several members of this genus have found medicinal uses in the treatment of rheumatism, diabetes, leprosy and as antiseptics and disinfectants. All parts are edible but rather more bitter and can cause diarrhea.

AIM OF THE STUDY

The present report was tentatively elucidated the structure of acylated and non-acylated polyoxypregnane glycosides from Caralluma quadrangula.

MATERIALS AND METHODS

The analyses were performed using an electrospray-ionization quadrupole time-of-flight (ESI-Q-TOF) mass spectrometer in both positive and negative ionization modes to explore fragmentation pathways. The antioxidant and prooxidant properties of the different mobility portions of human plasma were evaluated in vitro using thiobarbituric acid reactive substance assay (TBARS).

RESULTS

The analyses showed sixty-five characteristic ion peaks which could be more efficient to assignment the aglycones and fragmentation sequences of sugar moieties. The used ionization modes provided consistent and/or complementary information for most of the pregnane glycosides, their fragmentation sequences, and their aglycones. A DFT Study was performed to elucidate the neutral loss of H₂O molecules sequences from aglycones and the esterification linkage.

CONCLUSIONS

This report could be useful to reduce material consuming and time in phytochemistry analysis of the different medicinal plants. The two portions significantly depleted TBARS were subjected to autoperoxidation assay in the presence of hydrogen peroxide.

Discovery of Polyoxypregnane Derivatives From Aspidopterys obcordata With Their Potential Antitumor Activity

The bioassay-guided phytochemical study of an ethnic medicinal plant Aspidopterys obcorda ta Hemsl. var. obcordata results in the isolation of eight new polyoxypregnane derivatives, named aspidatasides A–H (1–8), along with ten known analogs (9–18). The series polyoxypregnane derivatives were screened for their cytoxic activity against HL-60 cells, and compound 2 showed the highest potency with an IC₅₀ 8.03 μM. Preliminary structure–activity relationship studies displayed that the sugar chain and double bond could notably impact their biological activity.

New Pregnane Glycosides Isolated from Caralluma hexagona Lavranos as Inhibitors of α-Glucosidase, Pancreatic Lipase, and Advanced Glycation End Products Formation

Caralluma hexagona Lavranos (Family Asclepiadaceae) is an endemic herb in Yemen and Saudi Arabia, traditionally used to treat diabetes, abdominal pain, and stomach ulcers. Different extracts, fractions, and main constituents of C. hexagona were evaluated for their inhibitory activity against key enzymes in diabetes and hyperlipidemia, i.e., α-glucosidase and pancreatic lipase. In addition, the antioxidative effect and inhibition of advanced glycation end products (AGEs) were also assayed. Using a bioguided approach, the crude aqueous, methanolic extracts, methylene chloride (CH₂Cl₂), Diaion HP20 50% MeOH (DCF-1), and 100% MeOH (DCF-2) fractions of C. hexagona were evaluated for their possible α-glucosidase and pancreatic lipase inhibition and antioxidant activity. In addition, inhibition of AGE generation using bovine serum albumin (BSA)-fructose, BSA-methylglyoxal, and arginine-methylglyoxal models was carried out. Moreover, the main constituents of the most active fraction were isolated and identified using different chromatographic and sprectroscopic methods. From the most active CH₂Cl₂ fraction, four new pregnane glycosides were isolated and identified as 12β-O-benzoyl 3β,8β,12β,14β,20-pentahydroxy-(20S)-pregn-5-ene-3-O-β-d-glucopyranosyl-(1 → 4)-O-β-d-digitaloside (1), 3β,8β,14β,20-tetrahydroxy-(20S)-pregn-5-ene-3-O-β-d-glucopyranosyl-(1 → 4)-O-β-d-digitaloside-20-O-3-isoval-β-d-glucopyranoside (2), 3β,8β,14β,20-tetrahydroxy-(20R)-pregn-5-ene-3-O-β-d-glucopyranosyl-(1 → 4)-O-β-d-digitaloside-20-O-3-isoval-4-benzoyl-β-d-glucopyranoside (3A), and 3β,8β,14β,20-tetrahydroxy-(20R)-pregn-5-ene-3-O-β-d-glucopyranosyl-(1 → 4)-O-β-d-digitaloside-20-O-3,4 di-benzoyl-β-d-glucopyranoside (3B). Among the tested samples, the highest trolox equivalent (TE) antioxidant capacity (TEAC) was observed for DCF-1 with values of 128.53 ± 5.07, 378.58 ± 5.19, and 106.71 ± 5.66 μM TE/mg using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant potential (FRAP) assays, respectively. The isolated apigenin-8-C-neohesperoside showed the highest antioxidant capacity (168.80 ± 1.80 and 278.21 ± 13.26 μM TE/mM) in DPPH and FRAP, respectively, while luteolin 4'-O-β-d-neohesperidoside had the highest TEAC (599.19 ± 9.57 μM TE/mM) in ABTS assay. Compounds 1, 2, and the mixture 3A and 3B inhibited α-glucosidase with IC₅₀ values of 0.92 ± 0.02, 0.67 ± 0.01, and 0.74 ± 0.02 mM, respectively. In the AGE assays, DCF-1 showed the highest inhibitory effect in BSA-fructose and arginine-methylglyoxal models with IC₅₀ values of 0.39 ± 0.02 and 0.77 ± 0.10 mg/mL, respectively. Among the isolated compounds, flavonoid compounds showed the highest antiglycation effect, while pregnanes revealed higher α-glucosidase inhibition. In conclusion, the current study revealed that C. hexagona is a promising Yemeni natural remedy, of which the major content of pregnane glycosides and flavonoids could be considered as a new therapeutic candidate targeting the metabolic syndrome.

Pregnane Glycosides

Pregnane glycosides constitute a class of compounds widely distributed in the plant kingdom. Many of them have shown either anticarcinogenic or cancer inhibitory properties, besides other useful biological activities. New chromatographic techniques and advances in spectroscopic and spectrometric methods have accelerated the purification and structure determination of novel glycosides of this series. A compilation of the pregnane glycosides isolated from 1995 until the middle of 2005, along with their physical data, structures and occurrence are presented in this review, which also summarizes, with suitable examples, recent developments in isolation and purification techniques, and structural elucidation using modern spectrometric methods like ESIMS and tandem mass spectrometry, and 2D NMR spectroscopic strategies. The reported anticancer and other biological activities of pregnane glycosides are also discussed.

Physiology of pepper fruit and the metabolism of antioxidants: chloroplasts, mitochondria and peroxisomes

BACKGROUND AND AIMS

Pepper (Capsicum annuum) contains high levels of antioxidants, such as vitamins A and C and flavonoids. However, information on the role of these beneficial compounds in the physiology of pepper fruit remains scarce. Recent studies have shown that antioxidants in ripe pepper fruit play a key role in responses to temperature changes, and the redox state at the time of harvest affects the nutritional value for human consumption. In this paper, the role of antioxidant metabolism of pepper fruit during ripening and in the response to low temperature is addressed, paying particular attention to ascorbate, NADPH and the superoxide dismutase enzymatic system. The participation of chloroplasts, mitochondria and peroxisomes in the ripening process is also investigated.

SCOPE AND RESULTS

Important changes occur at a subcellular level during ripening of pepper fruit. Chloroplasts turn into chromoplasts, with drastic conversion of their metabolism, and the role of the ascorbate-glutathione cycle is essential. In mitochondria from red fruits, higher ascorbate peroxidase (APX) and Mn-SOD activities are involved in avoiding the accumulation of reactive oxygen species in these organelles during ripening. Peroxisomes, whose antioxidant capacity at fruit ripening is substantially affected, display an atypical metabolic pattern during this physiological stage. In spite of these differences observed in the antioxidative metabolism of mitochondria and peroxisomes, proteomic analysis of these organelles, carried out by 2-D electrophoresis and MALDI-TOF/TOF and provided here for the first time, reveals no changes between the antioxidant metabolism from immature (green) and ripe (red) fruits.

CONCLUSIONS

Taken together, the results show that investigation of molecular and enzymatic antioxidants from cell compartments, especially chloroplasts, mitochondria and peroxisomes, is a useful tool to study the physiology of pepper fruit, particularly in the context of expanding their shelf-life after harvest and in maintaining their nutritional value.

A review on ethnobotany, phytochemistry and pharmacology of plant genus C aralluma R. Br

Objectives

C aralluma is a xerophytic genus used as traditional medicine for the treatment of diabetes, inflammation, leprosy, obesity and rheumatism. Objectives of this review are to establish a relationship between traditional uses and scientific studies by critically evaluating the available fragmented literature on ethnobotany, pharmacology, phytochemistry and toxicology of genus Caralluma.

Key findings

Ethnomedical uses of Caralluma have been recorded from various countries such as China, India, Iran and Pakistan for six major classes of diseases including diabetes and gastrointestinal disorders. This review indicated the efficacy of genus Caralluma in several in vitro and in vivo pharmacological properties such as antimicrobial, antioxidant and anticancer activity. These bioactivity might be due to the presence of certain classes of compounds in genus Caralluma including pregnane glycosides, flavonoid glycosides and flavones.

Summary

Traditional uses and scientific evaluation of Caralluma indicates that it is one of the most widely used genus in some parts of the world. Further studies on the structural activity relationship of some of the isolated compound may improve their biological potency as well as scientific exploitation of traditional uses of the genus.

Synthesis and anti-cancer evaluation of steroidal diglycoside–pyrazoline hybrids

A new series of pyrazoline-steroidal diglycoside hybrids were synthesized via catalyzed cyclocondensation of the corresponding chalcones, screened for in vitro cytotoxic activity and the SAR deduced.

Safety Assessment of a Hydroethanolic Extract of Caralluma fimbriata

This toxicological assessment evaluated the safety of a hydroethanolic extract prepared from Caralluma fimbriata (CFE), a dietary supplement marketed worldwide as an appetite suppressant. Studies included 2 in vitro genotoxicity assays, a repeated dose oral toxicity study, and a developmental study in rats. No evidence of in vitro mutagenicity or clastogenicity surfaced in the in vitro studies at concentrations up to 5000 μg of extract/plate (Ames test) or 5000 μg of extract/mL (chromosomal aberration test). No deaths or treatment-related toxicity were seen in the 6-month chronic oral toxicity study in Sprague-Dawley rats conducted at 3 doses (100, 300, and 1000 mg/kg body weight (bw)/d). The no observed effect level for CFE in this study was considered to be 1000 mg/kg bw/d. A prenatal developmental toxicity study conducted at 3 doses (250, 500, and 1000 mg/kg bw/d) in female Sprague-Dawley rats resulted in no treatment-related external, visceral, or skeletal fetal abnormalities, and no treatment-related maternal or pregnancy alterations were seen at and up to the maximum dose tested. CFE was not associated with any toxicity or adverse events.

Acylated pregnane glycosides from Caralluma sinaica

Caralluma sinaica is sold on local markets of Saudi Arabia for various health benefits however no phytochemical study has specifically been performed on this species. NMR and UHPLC-ESI-TOF-MS profilings of the ethanolic extract of the whole plant reveal a very complex phytochemical composition dominated by pregnanes. Detailed information on its constituents was obtained after isolation. Six pregnane glycosides were obtained and characterized based on the extensive spectroscopic analysis (including IR, ¹H NMR, ¹³C NMR and MS data), in addition to ten known compounds (seven pregnanes and three flavonoids). The compounds were identified as 12β-O-benzoyl-20-O-acetyl boucerin-3-O-6-deoxy-3-O-methyl-β-D-glucopyranosyl-(1-->4)-β-D-cymaropyranosyl-(1-->4)-β-D-cymaropyranoside, 12β-O-tigloyl-20-O-acetyl boucerin-3-O-β-D-glucopyranosyl-(1-->4)-β-D-cymaropyranoside, 12β-O-benzoyl-20-O-acetyl boucerin-3-O-β-D-glucopyranosyl-(1-->4)-β-D-digitalopyranosyl-(1-->4)-β-D-cymaropyranosyl-(1-->4)-β-D-cymaropyranoside, 12β-O-benzoyl-20-O-acetyl boucerin-3-O-β-D-glucopyranosyl-(1-->4)-hevetopyranosyl-(1-->4)-β-D-cymaropyranosyl-(1-->4)-β-D-cymaropyranoside, 12β-O-benzoyl-20-O-tigloyl boucerin-3-O-β-D-glucopyranosyl-(1-->4)-β-D-cymaropyranoside, 12β-20-O-dibenzoyl boucerin-3-O-β-D-glucopyranosyl-(1-->4)-β-D-cymaropyranosyl-(1-->4)-β-D-cymaropyranoside. Finally, the isolated compounds were evaluated for their quinone reductase induction.

Novel acylated steroidal glycosides from Caralluma tuberculata induce caspase-dependent apoptosis in cancer cells

AIM OF THE STUDY

Pregnane glycosides are potent cytotoxic agents which may represent new leads in the development of anti-tumour drugs, particularly in the treatment of breast cancer, because of the structural similarity to estrogenic agonists. Caralluma species are natural sources of a wide variety of pregnane glycosides. The aim of the study was to isolate, using an activity-guided fractionation approach, novel pregnane glycosides for testing on breast cancer and other tumour lines.

MATERIALS AND METHODS

The effect of crude extracts, specific organic fractions and isolated compounds from Caralluma tuberculata was tested on the growth and viability of MCF-7 estrogen-dependent, and MDA-MB-468 estrogen-independent breast cancer cells, Caco-2 human colonic cells, HUVECs and U937 cells. Neutral red uptake and MTT assays were used. Apoptosis was detected by Western blot of poly-(ADP ribose) polymerase (PARP) as were other markers of nuclear fragmentation (DNA ladder assay, staining of cells with nuclear dye DAPI). The involvement of caspases was investigated using the pan-caspase inhibitor Z-VAD-FMK.

RESULTS

The ethyl acetate fraction of Caralluma tuberculata was found to be the most potent anti-proliferative fraction against all three cancer cell lines. Two novel steroidal glycosides were isolated from the active fraction after a series of chromatographic experiments. The structure of the isolated compounds was elucidated solely based on 2D-NMR (HMBC, HETCOR, DQF-COSY) and MS spectral analysis as compound 1: 12-O-benzoyl-20-O-acetyl-3β,12β,14β,20β-tetrahydroxy-pregnan-3-ylO-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl-(1 → 4)-3-methoxy-β-D-ribopyranoside, and as compound 2: 7-O-acetyl-12-O-benzoyl-3β,7β,12β,14β-tetrahydroxy-17β-(3-methylbutyl-O-acetyl-1-yl)-androstan-3-ylO-β-D-glucopyranosyl-(1 → 4)-6-deoxy-β-D-allopyranosyl-(1 → 4)-β-D-cymaropyranosyl-(1 → 4)-β-D-cymapyranosyl-(1→ 4)-β-D-cymaropyranoside. Compound 1 (pregnane glycoside) and compound 2 (androstan glycoside) induced apoptosis at <25 μM after 48 h as assessed by cell shrinkage, PARP cleavage, DNA fragmentation, and reversal with the caspase inhibitor.

CONCLUSIONS

Two novel steroid glycosides isolated from Caralluma tuberculata possess moderate, micromolar cytotoxic activity on breast cancer and other cells in vitro, which may indicate a source of activity in vivo of interest to future drug design.

Acylated pregnane glycosides from Caralluma tuberculata and their antiparasitic activity

Five pregnane glycosides were isolated from Caralluma tuberculata (1-5), in addition to a known one (russelioside E, 6). The structures of the isolated compounds were elucidated by the analysis of NMR data and FAB-MS experiments. All the isolated compounds were tested for their antimalarial and antitrypanosomal activities as well as their cytotoxicity against human diploid embryonic cell line (MRC5).

Acylated pregnane glycosides from Caralluma russeliana

The chloroform extract of the aerial parts of Caralluma russeliana yielded four acylated pregnane glycosides, namely russeliosides E-H, three were found now. The structures of the compounds were elucidated using MS, 1H NMR, 13C NMR, 1H-1H COSY, HMQC, NOESY and HMBC experiments.

Penicillosides A-C, C-15 oxypregnane glycosides from Caralluma penicillata

The chloroform fraction of the defatted ethanol extract from the aerial parts of Caralluma penicillata yielded three C-15 oxypregnane glycosides, penicillosides A-C. Their structures were established by a combination of spectroscopic methods.

Pregnane glycosides from Caralluma russeliana

The aerial parts of Caralluma russeliana yielded four new pregnane glycosides, russeliosides A-D (1-4), in addition to a known flavone glycoside, luteolin 4'-O-beta-D-neohesperidoside. The structures of compounds 1-4 were elucidated using a combination of spectroscopic methods.

Four new steroids from two octocorals

In search of analogues of isogosterones A-D (1-4), a group of antifouling 13,17-seco-steroids found in octocorals of the order Alcyonacea, we have isolated four new steroids possessing aromatic, enone, or dienone A-rings from two octocorals, Alcyonium gracillimum and Dendronephthya sp. These compounds, 3-methoxy-19-norpregna-1,3, 5(10),20-tetraene (5), 3-(4-O-acetyl-6-deoxy-beta-galactopyranosyloxy)-19-norpregna-1,3, 5(10),20-tetraene (6), 22,23-dihydroxycholesta-1,24-dien-3-one (7), and methyl 3-oxochola-4,22-dien-24-oate (8), showed no antifouling activity against barnacle (Balanus amphitrite) larvae, but lethality to barnacle larvae at a concentration of 100 &mgr;g/mL (LD(100)).

Acylated C-21 steroidal bisdesmosidic glycosides from Caraluma umbellata

From the whole plant of Caraluma umbellata, three new C-21 steroidal glycosides, named as carumbellosides III-V, were isolated and their structures elucidated by extensive spectroscopic experiments, devoid of any derivatisation, as caralumagenin 3-O-beta-D-glucopyranosyl(1-->4)-beta-D-digitalopyranoside-20-O-be ta- D-glucopyranoside, caralumagenin 3-O-beta-D-glucopyranosy(1-->4)- beta-D-digitalopyranoside-20-O-(2-O- benzoyl)-beta-D-glucopyranoside and caralumagenin 3-O-[6-O-benzoyl-beta-D-glucopyranosyl(1-->4)]-beta-D- digitalopyranoside-20-O-(2-O-benzoyl)-beta-D-glucopyranoside. The determination of the absolute configuration of the aglycone as (20 R), the conformations of the sugars and the unambiguous assignments of their NMR spectroscopic signals were achieved by a combination of 2D-NMR techniques. The isolates were devoid of significant cytotoxity in the UIC human cancer cell panel.