Steroidal glycoalkaloids from Solanum nigrum target cytoskeletal proteins: an in silico analysis

Background

Solanum nigrum (black nightshade; S. nigrum), a member of family Solanaceae, has been endowed with a heterogeneous array of secondary metabolites of which the steroidal glycoalkaloids (SGAs) and steroidal saponins (SS) have vast potential to serve as anticancer agents. Since there has been much controversy regarding safety of use of glycoalkaloids as anticancer agents, this area has remained more or less unexplored. Cytoskeletal proteins like actin play an important role in maintaining cell shape, synchronizing cell division, cell motility, etc. and along with their accessory proteins may also serve as important therapeutic targets for potential anticancer candidates. In the present study, glycoalkaloids and saponins from S. nigrum were screened for their interaction and binding affinity to cytoskeletal proteins, using molecular docking.

Methods

Bioactivity score and Prediction of Activity Spectra for Substances (PASS) analysis were performed using softwares Molinspiration and Osiris Data Explorer respectively, to assess the feasibility of selected phytoconstituents as potential drug candidates. The results were compared with two standard reference drugs doxorubicin hydrochloride (anticancer) and tetracycline (antibiotic). Multivariate data obtained were analyzed using principal component analysis (PCA).

Results

Docking analysis revealed that the binding affinities of the phytoconstituents towards the target cytoskeletal proteins decreased in the order coronin>villin>ezrin>vimentin>gelsolin>thymosin>cofilin. Glycoalkaloid solasonine displayed the greatest binding affinity towards the target proteins followed by alpha-solanine whereas amongst the saponins, nigrumnin-I showed maximum binding affinity. PASS Analysis of the selected phytoconstituents revealed 1 to 3 violations of Lipinski’s parameters indicating the need for modification of their structure-activity relationship (SAR) for improvement of their bioactivity and bioavailability. Glycoalkaloids and saponins all had bioactivity scores between −5.0 and 0.0 with respect to various receptor proteins and target enzymes. Solanidine, solasodine and solamargine had positive values of druglikeness which indicated that these compounds have the potential for development into future anticancer drugs. Toxicity potential evaluation revealed that glycoalkaloids and saponins had no toxicity, tumorigenicity or irritant effect(s). SAR analysis revealed that the number, type and location of sugar or the substitution of hydroxyl group on alkaloid backbone had an effect on the activity and that the presence of α-L-rhamnopyranose sugar at C-2 was critical for a compound to exhibit anticancer activity.

Conclusion

The present study revealed some cytoskeletal target(s) for S. nigrum phytoconstituents by docking analysis that have not been previously reported and thus warrant further investigations both in vitro and in vivo.

The synthesis of solasodine F-homo-analogues

An efficient synthesis of F-homosolasodine analogues containing the 5/7 spirohemiaminal moiety was elaborated. The method benefited from an easy opening of diosgenin F-ring and the introduction of a cyano group in position 26.

An UPLC-MS/MS method for determination of solasonine in rat plasma and its application of a pharmacokinetic and bioavailability study

Solasonine, a known glycoalkaloid, is a potential anti-cancer agent. In this work, a simple, sensitive and fast ultra performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the quantitative determination of solasonine in rat plasma. Plasma samples were processed with a protein precipitation. The separation was achieved by an ACQUITY HSS T3 (100×2.1mm, 1.8μm) column with a gradient mobile phase consisting of 0.1% formic acid and acetonitrile. Detection was carried out using positive-ion electrospray tandem mass spectrometry via multiple reaction monitoring (MRM). The validated method had an excellent linearity in the range of 0.1-500ng/mL (R(2)>0.994) with a low limit of detection (0.1ng/mL) and lower limit of quantification (0.5ng/mL). The extraction recovery was in the range of 92.4-94.9% for solasonine and 91.9% for dendrobine (internal standard, IS). The intra- and inter-day precision was below 9.8% and accuracy was from 86.0% to 94.3%. No notable matrix effect and astaticism was observed for solasonine. The method has been successfully applied to a pharmacokinetic and bioavailability study of solasonine in rats for the first time, which provides the basis for the further development and application of solasonine.

Bioactivities of glycoalkaloids and their aglycones from Solanum species

Potatoes, tomatoes, and aubergines are all species of the Solanum genus and contain a vast array of secondary metabolites including calystegine alkaloids, phenolic compounds, lectins, and glycoalkaloids. Glycoalkaloids have been the subject of many literature papers, occur widely in the human diet, and are known to induce toxicity. Therefore, from a food safety perspective further information is required regarding their analysis, toxicity, and bioavailability. This is especially important in crop cultivars derived from wild species to prevent glycoalkaloid-induced toxicity. A comprehensive review of the bioactivity of glycoalkaloids and their aglycones of the Solanum species, particularly focused on comparison of their bioactivities including their anticancer, anticholesterol, antimicrobial, anti-inflammatory, antinociceptive, and antipyretic effects, toxicity, and synergism of action of the principal Solanum glycoalkaloids, correlated to differences of their individual molecular structures is presented.

Efficient Synthesis of Solasodine,O-Acetylsolasodine, and Soladulcidine as Anticancer Steroidal Alkaloids

An efficient synthesis of the steroidal alkaloids solasodine (1), O-acetylsolasodine (2), and soladulcidine (3) starting from easily available diosgenin and tigogenin in five or six steps (overall yield 25, 24, and 28%, resp.) is described. Moreover, our synthetic route provides a selective modification at C(3) of 1 and related compounds in order to carry out lead optimization on these natural antitumor steroidal alkaloids.