Steroidal alkaloids efficient aromatase inhibitors with potential for the treatment of postmenopausal breast cancer

Chemical constituents from Carica papaya Linn. leaves as potential cytotoxic, EGFRwt and aromatase (CYP19A) inhibitors; a study supported by molecular docking

The phytochemical investigation of the hydromethanolic extract of Carica papaya Linn. leaves (Caricaceae) resulted in the isolation and characterization of ten compounds, namely; carpaine (1), methyl gallate (2), loliolide (3), rutin (4), clitorin (5), kaempferol-3-O-neohesperidoside (6), isoquercetin (7), nicotiflorin (8) and isorhamnetin-3-O-β-d-glucopyranoside (9). The compounds 2, 3, 5-7 and 9 were isolated for the first time from the genus Carica. An in vitro breast cancer cytotoxicity study was evaluated with an MCF-7 cell line using the MTT assay. Methyl gallate and clitorin demonstrated the most potent cytotoxic activities with an IC₅₀ of 1.11 ± 0.06 and 2.47 ± 0.14 μM, respectively. Moreover, methyl gallate and nicotiflorin exhibited potential EGFR^wt kinase inhibition activities with an IC₅₀ of 37.3 ± 1.9 and 41.08 ± 2.1 nM, respectively, compared with the positive control erlotinib (IC₅₀ = 35.94 ± 1.8 nM). On the other hand, clitorin and nicotiflorin displayed the strongest aromatase kinase inhibition activities with an IC₅₀ of 77.41 ± 4.53 and 92.84 ± 5.44 nM, respectively. Clitorin was comparable to the efficacy of the standard drug letrozole (IC₅₀ = 77.72 ± 4.55). Additionally, molecular docking simulations of the isolated compounds to EGFR and human placental aromatase cytochrome P450 (CYP19A1) were evaluated. Methyl gallate linked with the EGFR receptor through hydrogen bonding with a pose score of -4.5287 kcal mol^-1 and RMSD value of 1.69 Å. Clitorin showed the strongest interaction with aromatase (CYP19A1) for the breast cancer receptor with a posing score of -14.2074 and RMSD value of 1.56 Å. Compounds (1-3) possessed a good bioavailability score with a 0.55 value.

The Role of Aromatase Enzyme in Hormone Related Diseases and Plant-Based Aromatase Inhibitors as Therapeutic Regimens

Medicinal plants have a long history of use as food and remedy in traditional and modern societies, as well as have been used as herbal drugs and sources of novel bioactive compounds. They provide a wide array of chemical compounds, many of which can not be synthesized via current synthesis methods. Natural products may provide aromatase inhibitory activity through various pathways and may act clinically effective for treating pathologies associated with excessive aromatase secretion including breast, ovarian and endometrial cancers, endometriosis, uterine fibroid, benign prostatic hyperplasia (BPH), prostate cancer, infertility, and gynecomastia. Recent studies have shown that natural products with aromatase inhibitory activity, could also be good options against secondary recurrence of breast cancer by exhibiting chemopreventive effects. Therefore, screening for new plant-based aromatase inhibitors may provide novel leads for drug discovery and development, particularly with increased clinical efficacy and decreased side effects.

The Alkaloid-Enriched Fraction of Pachysandra terminalis (Buxaceae) Shows Prominent Activity against Trypanosoma brucei rhodesiense

In the course of our studies on antiprotozoal natural products and following our recent discovery that certain aminosteroids and aminocycloartanoid compounds from Holarrhena africana A. DC. (Apocynaceae) and Buxus sempervirens L. (Buxaceae), respectively, are strong and selective antitrypanosomal agents, we have extended these studies to another plant, related to the latter-namely, Pachysandra terminalis Sieb. and Zucc. (Buxaceae). This species is known to contain aminosteroids similar to those of Holarrhena and structurally related to the aminocycloartanoids of Buxus. The dicholoromethane extract obtained from aerial parts of P. terminalis and, in particular, its alkaloid fraction obtained by acid-base partitioning showed prominent activity against Trypanosoma brucei rhodesiense (Tbr). Activity-guided fractionation along with extended UHPLC-(+)ESI QTOF MS analyses coupled with partial least squares (PLS) regression modelling relating the analytical profiles of various fractions with their bioactivity against Tbr highlighted eighteen constituents likely responsible for the antitrypanosomal activity. Detailed analysis of their (+)ESI mass spectral fragmentation allowed identification of four known constituents of P. terminalis as well as structural characterization of ten further amino-/amidosteroids not previously reported from this plant.

Targeting cell cycle by β-carboline alkaloids in vitro: Novel therapeutic prospects for the treatment of cancer

Cell cycle dysregulation is the mainstay of aberrant cell proliferation, which leads to tumor progression. Mutations in tumor cells initiate various dysregulated pathways and spontaneous over-proliferation with genomic/chromosomal instability. Despite advances in cancer therapy, it has remained a medicinal challenge to treat. Besides, the complexity of pathophysiological pathways behind cancer raises the need for novel multi-target agents, possessing fewer side effects. Alkaloid-based therapies have been explored so far to target cell division in cancer, including vinca alkaloids. As a class of hopeful β-carboline derivatives, growing evidence has indicated their auspicious roles in combating cancer by inhibiting topoisomerase (TOPO), kinesin Eg5, telomerase, cyclin-dependent kinase (CDK), IκB kinase (IKK), and polo-like kinase-1 (PLK1) in the transition phases of cell cycle. In this review, in vitro potential of β-carboline has been revealed through targeting cell division cycle at different phases. In conclusion, β-carboline alkaloids could be introduced as novel candidates in cancer therapy.

Pharmacological Modulation of Steroid Activity in Hormone-Dependent Breast and Prostate Cancers: Effect of Some Plant Extract Derivatives

The great majority of breast and prostate tumors are hormone-dependent cancers; hence, estrogens and androgens can, respectively, drive their developments, making it possible to use pharmacological therapies in their hormone-dependent phases by targeting the levels of steroid or modulating their physiological activity through their respective nuclear receptors when the tumors relapse. Unfortunately, at some stage, both breast and prostate cancers become resistant to pharmacological treatments that aim to block their receptors, estrogen (ER) or androgen (AR) receptors, respectively. So far, antiestrogens and antiandrogens used in clinics have been designed based on their structural analogies with natural hormones, 17-β estradiol and dihydrotestosterone. Plants are a potential source of drug discovery and the development of new pharmacological compounds. The aim of this review article is to highlight the recent advances in the pharmacological modulation of androgen or estrogen levels, and their activity through their cognate nuclear receptors in prostate or breast cancer and the effects of some plants extracts.