Detailed chemical studies on the roots of Piper sarmentosum and Piper nigrum have resulted in several alkaloids. The roots of P. sarmentosum gave a new aromatic compound, 1-nitrosoimino-2,4,5-trimethoxybenzene (1). Piper nigrum roots gave pellitorine (2), (E)-1-[3',4'-(methylenedioxy)cinnamoyl]piperidine (3), 2,4-tetradecadienoic acid isobutyl amide (4), piperine (5), sylvamide (6), cepharadione A (7), piperolactam D (8) and paprazine (9). Structural elucidation of these compounds was achieved through NMR and MS techniques. Cytotoxic activity screening of the plant extracts indicated some activity.
Pellitorine (1), which was isolated from the roots of Piper nigrum, showed strong cytotoxic activities against HL60 and MCT-7 cell lines. Microbial transformation of piperine (2) gave a new compound 5-[3,4-(methylenedioxy)phenyl]-pent-2-ene piperidine (3). Two other alkaloids were also found from Piper nigrum. They are (E)-1-[3',4'-(methylenedioxy)cinnamoyl]piperidine (4) and 2,4-tetradecadienoic acid isobutyl amide (5). These compounds were isolated using chromatographic methods and their structures were elucidated using MS, IR and NMR techniques.
Inhibition of cytochrome P450 (P450) enzymes (CYP) has been shown to lower the metabolism of drugs that are P450 substrates and to consequently alter their pharmacokinetic profiles. Curcumin (CUR), piperine (PIP), and capsaicin (CAP) are spice components (SC) that inhibit the activities of a range of P450 enzymes, but the selection of which SC to be prioritized for further development as an adjuvant will depend on the ranking order of the inhibitory potential of the SCs on specific P450 isozymes. We used common human recombinant enzyme platforms to provide a comparative evaluation of the inhibitory activities of CUR, PIP, and CAP on the principal drug-metabolizing P450 enzymes. SC-mediated inhibition of CYP3A4 was found to rank in the order of CAP (IC501.84 ± 0.71 µM) ∼ PIP (2.12 ± 0.45 µM) > CUR (11.93 ± 3.49 µM), while CYP2C9 inhibition was in the order of CAP (11.95 ± 4.24 µM) ∼ CUR (14.58 ± 4.57 µM) > PIP (89.62 ± 9.17 µM). CAP and PIP were significantly more potent inhibitors of CYP1A2 (IC502.14 ± 0.22 µM and 14.19 ± 4.15 µM, respectively) than CUR (IC50> 100 µM), while all three SCs exhibited weak activity toward CYP2D6 (IC5095.42 ± 12.09 µM for CUR, 99.99 ± 5.88 µM for CAP, and 110.40 ± 3.23 µM for PIP). Of the three SCs, CAP thus has the strongest potential for further development into an inhibitor of multiple CYPs for use in the clinic. Data from this study are also useful for managing potential drug-SC interactions.