Enhancing extraction efficiency of carpaine in Carica papaya L. leaves: coupling acid-base extraction with surfactant-assisted micro-flotation

Abstract

Carpaine, a major alkaloid in papaya leaves, has considerable cardiovascular benefits alongside its notable effects on muscle relaxation when utilized in medicine. In this study, the coupling of acid-base extraction and flotation was developed to completely remove the use of toxic solvents. This method entails the extraction of carpaine from Carica papaya L. leaves using hot water extraction alongside ultrasound-assisted extraction followed by the condensation of the species using surfactant-assisted flotation. The acid-base extraction was applied to alter the solubility of carpaine as desired at different stages of the process. The results showed that the carpaine extraction yield using all the treatments in conjunction was significantly higher compared to the control samples in which the acid-base extraction or flotation was not applied. The TLC and GC-FID results suggested that the bubbles introduced during the flotation were highly specific toward their interactions with carpaine in its hydrophobic complex form. The quantity of carpaine extracted using our method, in comparison to the amount of carpaine obtained using a different method from a previous study that utilized ethanolic extraction, exhibited a 2.32-fold greater extraction yield. This work demonstrates the importance of flexible utilization of both surface and bulk chemistry in achieving an improved solution for a technical problem.

Fig. 1. Chemical structure of carpaine.

Fig. 2. Surface tension reduction due to saponin, CTAB and a combination of both; deionized water (DI), DI with CTAB (0.075 mM) (CTAB), papaya extract (PE), and papaya extract with CTAB (0.075 mM) (PE+CTAB).

Fig. 3. Surface tension comparison between the extract containing CTAB and the extract containing SDS. Papaya extract (PE), papaya extract with CTAB (0.075 mM) (PE+CTAB), papaya extract with SDS (0.15 mM) (PE+SDS).

Fig. 4. Thin-layer chromatography analysis for carpaine visualization; (a) identification of carpaine; (b) comparison of carpaine in treatment sample with all controls, standard carpaine (S), carpaine–CTAB complex (C), carpaine–CTAB complex mixed with foam sample (C+F), control without flotation (B), foam sample (F), control without pre-incubation pH adjustment (C1), control without CTAB (C2), and control without pre-flotation pH adjustment (C3).

Fig. 5. Standard curve of carpaine.

Fig. 6. Carpaine extraction yield quantified by GC-FID; foam sample (F), control without acidification (C1), control without CTAB (C2), and control without basification.

Fig. 7. Carpaine–CTAB complex via electrostatic interaction (logP = 13.49).

Fig. 8. TLC illustration of carpaine and carpaine–CTAB complexes. Standard carpaine (S), carpaine–CTAB complex (C).

Fig. 9. GC-FID chromatogram of extracted carpaine after flotation.

Fig. 10. Enhanced carpaine liberation during maceration in an acidic environment.

Fig. 11. Confirmation of the effect of CTAB on the polarity of carpaine complexes; 4-fold diluted foam sample (F-1/4), 4-fold diluted control without CTAB sample (C2-1/4), foam sample (F), and control without CTAB (C2).

Fig. 12. Different interaction modes of carpaine complexes with CTAB and SDS.

Fig. 13. Correlation between dilute concentrations and carpaine signals of SDS foam sample.