Cucurbitacins extraction

Some cucurbitacins have been reported to be antifertility agents. The enriched cucurbitacin extract obtained from Wilbrandia sp. was tested for its potential antifertility effects with different experimental protocols including those involving estrus cycle, implantation, abortifacient, and estrogenic/antiestrogenic activities. The extract suppressed the number of... 

The total contents of cucurbitacins are generally lower in the extracts 1-4 than in Tayuae (5) and Bryoniae radix extracts (6-8). 

A second example of this same NCI procedure resulted in the rapid identification of cucurbitacin D from a novel source (55). The pattern of cytotoxic activity observed from a crude extract of Gonystylus keithii against renal, brain, and melanoma subpanels correlated strongly with the pattern observed earlier for purified cucurbitacins B, E, and I (Scheme 5). This bioprofile indication led to the expeditious fractionation and identification of cucurbitacin D as the anticancer active component in the extract. 

Some active species have been studied and their pharmacological activity confirmed in different experimental models. In general, the active fractions of such plants were those containing cucurbitacins, as demonstrated by Rios et al. [10] in their work with Cayaponia tayuya roots. This species is used in the Amazon region of South America as an analgesic, anti-inflammatory, and anti-rheumatic agent while the extracts of this species are widely employed in the treatment of skin disorders such as dermatosis and other irritations. The chloroform fraction obtained from the active root methanol extract was found to be more active than the ethyl acetate and butanol fractions. Subsequent phytochemical analysis demonstrated that the chloroform fraction is rich in cucurbitacins, whereas the ethyl acetate and butanol fractions are principally comprised of C-glycosil flavonoids [10]. 

Thin-layer chromatography (TLC) is a good method for detecting the presence of cucurbitacins in a plant extract. The best results to date have been achieved using high-performance TLC (HPTLC) plates [41] with silica gel and chloroform-methanol (95 10) (Table 1) or toluene-ethyl acetate (25 75) as mobile phases [3,11]. Reversed-phase (RP) HPTLC plates with methanol-water (7 3) have also been used to separate cucurbitacins [3]. The compounds are easily detected with vanillin-sulphuric acid or vanillin-phosphoric acid reagents and ultraviolet light (UV) at 365 nm [11]. 

HPLC also seems to be a good method for separating cucurbitacin mixtures [3]. Since these compounds tend to exhibit at least medium polarity, an RP system is the most appropriate stationary phase (Cjg column), with a linear gradient from 20% to 50% of acetonitrile [3] or methanol [42,44] in water being the best mobile phases for separation of both free-aglycones and glycosides. In this case, previous purification of samples by means of a solid-phase extraction (SPE) is advisable. The addition of 0.01% of trifluoroacetic acid (TFA) improves the separation and reduces complications from interfering substances [3]. 

The dichloromethane extract from Wilbrandia ebracteata (p.o.) significantly reduced the paw elevation time (1 mg/kg) and cell influx (10 mg/kg) in zymosan-induced arthritis in rats. The same extract inhibited COX-2 activity, as measured by PGE2 production, without affecting that of COX-1. Moreover, nitrite release was clearly and significantly reduced at a dose of 10 mg/kg (p.o.). The analysis of the pharmacological data, together with the HPLC analysis of the extracts, points to an anti-inflammatory effect based on an associated reduction in nitric oxide (NO) release and COX-2 inhibition by the cucurbitacins... 

In another paper, Rios et al. [10] reported the anti-inflammatory activity of the chloroform extract from Cayaponia tayuya, which exhibited a high potency against carrageenan-induced mouse paw edema, with an ED50 of 122.5 mg/kg (p.o.) and 27.8 (i.p.). From the active extract, Recio et al. [43] isolated two cucurbitacins which were identified as cucurbitacin R and 23,24-dihydrocucurbitacin B, Fig. (7). 

Different extracts obtained from species of Wilbrandia exhibited antiinflammatory activity when assayed in different experimental models of inflammation, such as carrageenan-induced rat hind paw edema, carrageenan-induced granuloma in rats, and acetic acid-induced vascular permeability in mice. The authors attributed the anti-inflammatory effect to the two nor-cucurbitacin glucosides isolated previously from the same source, namely cucurbitacins WGi and WG2, Fig. (10) [6]. 

From the anti-inflammatory, antipyretic, analgesic, and antioxidant extract of Kageneckia oblonga, Delporte et al. [13] isolated two cucurbitacins which were assayed as potential antioxidants and also as inhibitors of enzymes implicated in inflammatory reactions. Isolated compounds, 23,24-dihydrocucurbitacin F and 3P-( 3-D-glucosyloxy)-16a,23a-epoxy-cucurbitan-5,24-diene-ll-one, Fig. (11), inhibited the production of superoxide anion as well as elastase release in stimulated human neutrophils. In addition, the compounds inhibited both nitrite and... 

Both the extracts containing cucurbitacins and the isolated compounds themselves have been reported as analgesic agents. The dichloromethane extract from Wilbrandia ebracteata roots administered i.p., for example, had an analgesic effect in the acetic acid writhing test in mice, reducing... 

Tn the case of the extract of Kageneckia oblonga, the authors established a relationship between cucurbitacins present in the extract and its antipyretic and analgesic activities, justifying a potential mechanism in which a decrease in PGE2 production through the inhibition of COX activity is implicated [13]. 

As was described above, Panossian et al. [57] demonstrated the adaptogenic activity of Bryonia alba roots in preclinical and clinical trials. The same authors [75] studied the potential mechanism responsible for these adaptogenic effects, focusing on the potential activity of cucurbitacin R-diglucoside, one of the constituents of the active extract. This compound had previously been found to increase the working capacity of mice, and also to increase the survival of mice infected with Staphylococcus aureus as well as that of X-ray irradiated rats. It also reduced stomach ulcers in immobilized rats [75]. 

Some studies hypothesize about the protection of cucurbitacins against soil borne fungal entomopathogens, both in the adult com rootworm and in the eggs laid in the soil. However, Martin et al. [84] demonstrated that cucurbitacins do not inhibit fungal growth, as seen by the fact that the sterilized extract containing them showed no activity. These authors thus hypothesize that the activity may actually be due to bacteria associated with the plants. 

In general, cucurbitacins and the extracts containing them are considered to be toxic, with the degree of toxicity depending on the plant material, type of extract, and the substitution partner of the compound. For example, exposure to the juice of the anti-inflammatory medicinal plant Ecbalium elaterium, especially in its undiluted form, often leads to a supposedly inflammatory irritation of mucous membranes [87]. These toxic effects seem to correspond to the juice s major active compound, cucurbitacin B. 

Further fractionation of the active ethanol extract of Desfontainia spinosa based on cytotoxicity has led to the discovery of two novel, cytotoxic glycosides of the parent, 11-deoxocucurbitacin I, named spinoside A (8) and spinoside B (9). The structures of 8 and 9 were established on the basis of extensive analysis of their high field NMR, NMR, high resolution mass spectra (FAB, FD, Cl, El) and chemical interconversions (ref. 57). The novel arabinopyranoside derivatives of 6 were less cytotoxic than the parent compound in the 9PS system. Cucurbitacins although highly cytotoxic have never demonstrated significant anticancer effects in vivo. 

In the TLC of Fig. 3c with solvent (b) detected at UV 366 nm appear the cucurbitacins of the extracts and the reference with distinct characteristic carmin red fluorescent colour as reported in the literature... 

The authentication of the Radix Trichosanthes kirilowii or Tr. rosthornii extracts can be confirmed by the TLC and HPLC-detection of the characteristic cucurbitacins. 

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