Flavonoids and a saponin from Spartium junceum

Hydroalcoholic extract of Spartium junceum L. flowers inhibits growth and melanogenesis in B16-F10 cells by inducing senescence

BACKGROUND

Ultraviolet light exposure generates, in human tissues, radical species, which represent the main cause of photo-aging, DNA damage and skin cancer onset. On the other hand, Mediterranean plants, being continuously subjected to high solar radiation levels, are naturally adapted to take on this type of abiotic stress, thanks to the production of antioxidant secondary metabolites. For these reasons, several plant extracts were documented to be excellent antineoplastic drugs.

PURPOSE

We investigated the potential antitumor activity of the flower extract obtained by Spartium junceum L., a Mediterranean shrub, correlating it with the plant metabolic profile.

STUDY DESIGN

After selecting the best extraction method to obtain as more secondary metabolites as possible from S. junceum flowers, we characterized the extract metabolic content. Then, by in vitro analyses, the antioxidant profile and the antineoplastic activity on B16-F10 murine melanoma cell of our extract were investigated.

METHODS

Spectrophotometric assays, HPLC-DAD and GC-MS analyses provided us information about flower extract composition and antioxidant activity. MTT assay and Trypan Blue exclusion test were performed to assess the extract toxicity and the viability, after treatments, of B16-F10 cancer cells and of C2C12 murine myoblasts. In vitro experiments (i.e. cytofluorimetry, protein analysis and qPCR) allowed us to analyze the effect of the plant extract on B16-F10 cell redox state, melanogenesis and cell cycle. Senescence induction was investigated by using a specific kit.

RESULTS

We observed that the hydroalcoholic extract of S. junceum flowers (HFE) strongly inhibited B16-F10 murine melanoma cell proliferation, while just a feeble effect was observed on C2C12 murine myoblasts. Moreover, we found that HFE exerted a pro-oxidant activity on melanoma cells, inhibited melanogenesis and caused cell cycle arrest in G2/M phase, inducing senescence. These anti-cancer properties of HFE could be related to the rich metabolic profile of the extract that we characterized by HPLC-DAD and GC-MS analyses.

CONCLUSION

This evidence suggests that S. junceum phytocomplex can be used as a selective, nontoxic, economic and easily available anticancer drug.

Saponins, classification and occurrence in the plant kingdom

Saponins are a structurally diverse class of compounds occurring in many plant species, which are characterized by a skeleton derived of the 30-carbon precursor oxidosqualene to which glycosyl residues are attached. Traditionally, they are subdivided into triterpenoid and steroid glycosides, or into triterpenoid, spirostanol, and furostanol saponins. In this study, the structures of saponins are reviewed and classified based on their carbon skeletons, the formation of which follows the main pathways for the biosynthesis of triterpenes and steroids. In this way, 11 main classes of saponins were distinguished: dammaranes, tirucallanes, lupanes, hopanes, oleananes, taraxasteranes, ursanes, cycloartanes, lanostanes, cucurbitanes, and steroids. The dammaranes, lupanes, hopanes, oleananes, ursanes, and steroids are further divided into 16 subclasses, because their carbon skeletons are subjected to fragmentation, homologation, and degradation reactions. With this systematic classification, the relationship between the type of skeleton and the plant origin was investigated. Up to five main classes of skeletons could exist within one plant order, but the distribution of skeletons in the plant kingdom did not seem to be order- or subclass-specific. The oleanane skeleton was the most common skeleton and is present in most orders of the plant kingdom. For oleanane type saponins, the kind of substituents (e.g. -OH, =O, monosaccharide residues, etc.) and their position of attachment to the skeleton were reviewed. Carbohydrate chains of 18 monosaccharide residues can be attached to the oleanane skeleton, most commonly at the C3 and/or C17 atom. The kind and positions of the substituents did not seem to be plant order-specific.

Anti-inflammatory and analgesic effects of Spartium junceum L. flower extracts: a preliminary study

Our objective was to study the anti-inflammatory and analgesic activity of extract of Spartium junceum L. flowers. Samples of flowers were collected from wild plants, dried, powdered, and extracted with hexane and methanol. The extracts were evaporated to dryness and then suspended in suitable solvent. They were then tested for anti-inflammatory activity in the carrageenin rat paw edema test and for analgesic activity in the Randall and Selitto mechanical pressure test and in the tail-flick test. Twenty-four hours after treatment, the gastric mucosa of each rat was observed macroscopically. Based on these results the hexane extract was fractioned by column chromatography, and the fractions obtained were tested in the same way. The results showed good anti-inflammatory activity only for a single fraction of the hexane extract, while all the extracts and all the other hexane fractions showed both peripheral and central analgesic activity. In rats treated with the tested compounds hyperemia and ulcers were absent. The data from this preliminary study reveal interesting pharmacological properties of S. junceum L. flowers extract related to the marked analgesic activity and the absence of gastric ulcerogenic activity.

A saponin with anti-ulcerogenic effect from the flowers of Spartium junceum

A new oleanene-type saponin with potent anti-ulcerogenic activity was isolated from the flowers of Spartium junceum. The various techniques of NMR spectral analysis, viz. 1H, 13C, DEPT, C-H COSY, H-H COSY, COLOC, NOESY, HMBC, HMQC, in conjunction with EI- and FAB-mass spectrometry, revealed that the structure of the isolated saponin was 3-O-[alpha-L-rhamnopyranosyl-(1-->2) -O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucuronopyranosyl]-3 beta,16beta,22 beta,24-tetrahydroxy-olean-12-ene and named as spartitrioside.