Bioactivity guided identification of sexual function restorative constituents of Carpolobia lutea G. Don roots in paroxetine-induced sexual dysfunction male rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Aqueous extract of Carpolobia lutea G. Don roots (AECLR) have been documented to restore sexual competence in sexual dysfunction male rats (SDMRs) without information on the ingredients responsible for such pharmacological effects and its mechanism of action.

AIM OF THE STUDY: The study aimed to identify the aphrodisiac bioactive agents in C. lutea roots and their mechanism of action.

MATERIALS AND METHODS: Two hundred and ten sexually active (that evinced a minimum of 60 % of all attempted cases of copulatory behaviour {Number of Mount (NM), Number of Intromission (NI) and Latency of Ejaculation (LE)} with receptive female rats within 15 min of observatory period) male rats (181.39 ± 6.15 g) were assigned into 3 experimental phases (n = 10/Group): partitioned fraction phase (70 male rats; Groups I-VII), column chromatographic fraction phase (90 male rats; Group I-IX) and mechanistic phase (male 50 rats; Groups I-V). Group I (Sham Control, SC), paroxetine-induced sexual dysfunction rats in Groups II (Negative Control, NC) and III (Positive Control, PC) were orally gavaged with distilled water (DW, 0.5 ml), DW and 7.14 mg/kg body weight (BW) of sildenafil citrate. The paroxetine-treated rats in other Groups received 141 mg/kg BW each of ethylacetate partitioned fraction (EAPF), n-butanol partitioned fraction, (nBPF), n-hexane partitioned fraction (nHPF), aqueous residual partitioned fraction (ARPF), aqueous residual column chromatographic fractions 1, 2 and 3 (ARCCF1, ARCCF2 and ARCCF3) and ethylacetate column chromatographic fractions 1, 2 and 3 (EACCF1, EACCF2 and EACCF3). Sexual behaviour parameters were monitored 24 h after 1, 3, 7, 14 and 28 daily doses whilst other biomolecules and clusters of genital reflexes were evaluated after 28-days of treatment. The most active, ARPF and EAPF were subjected to column chromatography, and eluents screened for biological activity. Chemical compounds in the most active ARCCF2 and EACCF2 were identified using high performance liquid chromatography after which their mechanism of sexual function restorative activities were evaluated in male rats.

RESULTS: paroxetine administration significantly (p < 0.05) lowered/decreased the NM, NI, number of ejaculation (NE), copulatory efficiency (CE), serum concentrations of follicle stimulating hormone (FSH), testosterone, dihydrotestosterone (DHT), luteinizing hormone (LH) and cluster of genital reflexes (CGR); prolonged the LE, latencies of mount (LM) and intromission (LI), and post interval ejaculation (PIE). The ARPF, EAPF, ARCCF1, ARCCF2, ARCCF3, EACCF1, EACCF2 and EACCF3 significantly (p < .05) and progressively increased the NM, NI, NE and CE and shortened the LM, LI, LE and PIE in a manner similar to the PC in the order: ARPF > EAPF > ARCCF2 > EACCF2 > PC > SC > EACCF1> EACCF3 > ARCCF1 > ARCCF3 > nBPF > nHPF, with ARPF, EAPF, ARCCF2 and EACCF2 displaying the most pronounced therapeutic effects. In addition, ARCCF2, ARCCF3, EACCF1, EACCF2 and EACCF3 significantly (p < .05) increased the PXT-treatment-related decreases in the CGR, FSH, testosterone, DHT and LH, with the most pronounced effects by ARCCF2 and EACCF2. The ARCCF2 which contained polygalasaponin XXVIII (1000 mg/ml) and EACCF2 that contained cinnamic acid (847. 8 mg/ml), quercetin (122.05 mg/ml) and kaempferol (30. 45 mg/ml) downregulated the 2 to 3-fold paroxetine-treatment related increases in serotonin, Gamma-amino butyric acid, acetylcholinesterase, phosphodiesterase 5, arginine and upregulated the 2-2.7-fold paroxetine-treatment related decreases in nitric oxide, acetylcholine and norepinephrine.

CONCLUSION: Polygalasaponin XXVIII and cinnamic acid-rich fraction of Carpolobia lutea roots restored sexual competence in the antidepressant-induced sexual dysfunction male rats via modulating the activities/levels of the reproductive hormones, neurotransmitters, enzymes and messenger molecules associated with sexual function in male rats. Polygalasaponin XXVIII and the constituents of cinnamic acid-rich fraction may offer therapeutic potential in the management of male sexual dysfunction in humans after toxicity studies and clinical trials.