Piper Nigrum is known as black pepper

Piper nigrum has a compound called piperine. A trademarked version of piperine is called Bioperine.

Brain health
Piperine, the main alkaloid of Thai black pepper, protects against neurodegeneration and cognitive impairment in animal model of cognitive deficit like condition of Alzheimer's disease.
Food Chem Toxicol. 2010; Chonpathompikunlert P, Wattanathorn J, Muchimapura S.Department of Physiology and Graduate School, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
Recently, numerous medicinal plants possessing profound central nervous system effects and antioxidant activity have received much attention as food supplement to improve cognitive function against cognitive deficit condition including in Alzheimer's disease condition. Based on this information, the effect of piperine, a main active alkaloid in fruit of Piper nigrum, on memory performance and neurodegeneration in animal model of Alzheimer's disease have been investigated. Adult male Wistar rats (180-220 g) were orally given piperine at various doses ranging from 5, 10 and 20mg/kg BW at a period of 2 weeks before and 1 week after the intracerebroventricular administration of ethylcholine aziridinium ion (AF64A) bilaterally. The results showed that piperine at all dosage range used in this study significantly improved memory impairment and neurodegeneration in hippocampus. The possible underlying mechanisms might be partly associated with the decrease lipid peroxidation and acetylcholinesterase enzyme. Moreover, piperine also demonstrated the neurotrophic effect in hippocampus. However, further researches about the precise underlying mechanism are still required.

Piper nigrum and histamine
Histamine release inhibitory activity of Piper nigrum leaf.
Biol Pharm Bull. 2008. Hirata N, Naruto S, Inaba K, Itoh K, Iinuma M, Matsuda H. Hirata N, Naruto S, Inaba K, Itoh K, Tokunaga M, Iinuma M, Matsuda H. School of Pharmacy, Kinki University, Higashiosaka, Osaka, Japan.
Oral administration of a methanolic extract of Piper nigrum leaf showed a potent dose-dependent inhibition of dinitrofluorobenzene (DNFB)-induced cutaneous reaction. Two lignans of piper nigrum extract, (-)-cubebin and (-)-3,4-dimethoxy-3,4-desmethylenedioxycubebin, were identified as major active principles having histamine release inhibitory activity.

Piper Nigrum research studies
Testosterone 5alpha-reductase inhibitory active constituents of Piper nigrum leaf.
Biol Pharm Bull. 2007. Hirata N, Iinuma M, Matsuda H. School of Pharmaceutical Sciences, Kinki University, Higashiosaka, Japan.
Previously we reported that Piper nigrum leaf extract showed a potent stimulation effect on melanogenesis and that (-)-cubebin (1) and (-)-3,4-dimethoxy-3,4-desmethylenedioxycubebin (2) were isolated as active constituents. As a part of our continuous studies on Piper species for the development of cosmetic hair-care agents, testosterone 5alpha-reductase inhibitory activity of aqueous ethanolic extracts obtained from several different parts of six Piper species, namely Piper nigrum, Piper methysticum, Piper betle, Piper kadsura, Piper longum, and Piper cubeba, were examined. Among them, the extracts of Piper nigrum leaf, Piper nigrum fruit and Piper cubeba fruit showed potent inhibitory activity. Activity-guided fractionation of Piper nigrum leaf extract led to the isolation of 1 and 2. Fruits of Piper cubeba contain 1 as a major lignan, thus inhibitory activity of the fruit may be attributable to 1. As a result of further assay on other known constituents of the cited Piper species, it was found that piperine, a major alkaloid amide of Piper nigrum fruit, showed potent inhibitory activity, thus a part of the inhibitory activity of Piper nigrum fruit may depend on piperine. The 5alpha-reductase inhibitory activities of 1 and piperine were found for the first time. In addition, the Piper nigrum leaf extract showed in vivo anti-androgenic activity using the hair regrowth assay in testosterone sensitive male C57Black/6CrSlc strain mice.

Piper species include
Piper longum herb
 

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