Iridoid-glycoside isolation and purification from Premna fulva leaves.

Premna fulva Craib, rich in iridoid glycosides, is widely used to treat periarthritis, osteoproliferation, pain, and other diseases. However, no studies have reported effective purification methods for obtaining iridoid glycosides as active materials. This paper describes an efficient strategy for separating iridoid glycosides from Premna fulva leaves using high-speed counter-current chromatography and preparative high-performance liquid chromatography. A two-phase solvent system, ethyl acetate/n-butanol/water (7.5:2.5:10, v/v), was selected for high-speed counter-current chromatography separation. The proposed method effectively separated and purified four iridoid glycosides and four lignans, including three new iridoid glycosides (4-6) and five known compounds (1-3, 7, 8), from Premna fulva leaves, indicating that high-speed counter-current chromatography combined with prep-HPLC can efficiently isolate catalpol derivatives from the genus Premna. Additionally, the in vitro anti-inflammatory activities of all isolated compounds were analyzed using lipopolysaccharide-stimulated RAW 264.7 cells, and the results indicated that six compounds (1 and 3-7) exhibited potential anti-inflammatory activities.

The bioactive amide alkaloids from the stems of Piper nigrum.

Piper nigrum is an important aromatic plant, and its fruits (black and white pepper) are commonly used as food additives and spices. However, its stems were disposed as wastes. This research comprehensively investigated bioactive alkaloids of the stems, eight new dimeric amide alkaloids and eight known compounds were obtained. All obtained compounds showed excellent anti-inflammatory activity. Additionally, the dimeric amide alkaloids enhanced the anticancer effect of paclitaxel against cervical cancer cells. These results demonstrate that the stems of P. nigrum could be the sustainable source of bioactive alkaloids for development and utilization in the food and health fields.

Alkaloids from Piper nigrum Synergistically Enhanced the Effect of Paclitaxel against Paclitaxel-Resistant Cervical Cancer Cells through the Downregulation of Mcl-1.

In the current study, nine amide alkaloids, including two new dimeric amides and a new natural product, were identified from Piper nigrum. Among them, seven compounds sensitized paclitaxel-resistant cervical cancer cells HeLa/PTX to paclitaxel. Piperine was a major component obtained from Piper nigrum, and its sensitization mechanism was investigated. Combination treatment enhanced cell apoptosis, which was mediated by downregulation of phospho-Akt and Mcl-1. Piperine (50 µM) combined with paclitaxel (200 nM) downregulated Mcl-1 protein expression with a decrease of 35.9 ± 9.5% ( P < 0.05). Moreover, overexpression of Mcl-1 attenuated the inhibitory effect of this combination. Furthermore, combination treatments of six dimeric amide alkaloids and paclitaxel all downregulated Mcl-1 protein expression with a decrease ranging from 23.5 ± 9.7% to 41.7 ± 7.2% ( P < 0.05). We reveal, for the first time, that dimeric amide alkaloids from plants possess a remarkable sensitization effect on cancer cells to paclitaxel.