What are the biological effects and delivery systems of capsaicin?

Introduction

CAP is traditionally used as an analgesic for topical treatment of muscle, joint and neuropathic pain, and exerts its effects by binding to the transient receptor potential vanilloid 1 (TRPV1) receptor located on neurotransmitter neurons in the peripheral nervous system. CAP has beneficial effects such as antioxidant, antimicrobial, anti-inflammatory, anticancer, anticancer, antitumor, anti-obesity, cardioprotective, gastroprotective and metabolic regulation. A recent study showed that CAP can regulate circadian rhythm disorders in HepG2 cells. In this review, Muwen Lu and Yong Cao from South China Agricultural University and Chi-Tang Ho from Rutgers University, USA, studied and discussed the beneficial biological functions of CAP and their underlying mechanisms, and evaluated various dietary CAP delivery systems based on their stability, loading efficiency, controlled release profile and bioavailability.

Biological Efficacy of Capsaicin

Analgesic effect

CAP is usually used as an external medicine to treat chronic pain such as osteoarthritis, rheumatoid arthritis, diabetic neuropathy, non-diabetic neuropathy and postherpetic neuralgia. Mechanistic studies have shown that CAP can selectively bind to TRPV1, a cation channel with high permeability to Ca2+ that can detect potentially harmful stimuli. After exposure to CAP, TRPV1 receptors are desensitized, resulting in reduced receptor function, which is also the reason for CAP-induced analgesia. In addition, CAP can also activate TRPV1 receptors, increase intracellular Ca2+ content, and release inflammatory neuropeptides (substance P). Through this calcium-dependent process, substance P is completely consumed, and primary afferent fibers are desensitized or even damaged to further painful stimuli (including thermal, mechanical and chemical toxicant stimuli), thereby achieving analgesic effects.

Anti-cancer effect

According to various studies, CAP has shown anti-cancer effects in various types of human cancers, including gastric cancer, breast cancer, lung cancer, prostate cancer, colorectal cancer, pancreatic cancer, etc. CAP can regulate the expression levels of genes and enzymes involved in cancer cell proliferation, cell cycle arrest, signal transduction, apoptosis and metastasis, thereby showing significant anti-tumor activity.

CAP anti-cancer mechanism

Anti-obesity effect

Studies have shown that CAP can inhibit lipogenesis and increase lipid oxidation in adipocytes; regulate hypothalamic satiety and suppress appetite by acting on gastrin; prevent weight gain by upregulating UCP2 and UCP3; and enhance heat production and maintain metabolic balance by regulating intestinal microbiota.

CAP's anti-obesity effect and its potential mechanism

Circadian-modulation effect

Circadian rhythms exist in almost all organisms, and circadian rhythm disorders can lead to metabolic syndrome, including hypertension, hyperlipidemia, insulin resistance, and atherosclerosis. The central circadian rhythm consists of multiple circadian oscillators, including two activators (CLOCK and BMAL1) and two inhibitors (PER and CRY), as well as other kinases and phosphatases. Plant hormones play an important role in the regulation of the circadian clock.

Improvement of CAP on circadian rhythm disorders in HepG2 cells

New CAP delivery system with higher bioavailability

Summary

As an analgesic, CAP has been widely used in ointments, gels, and patches to relieve pain. Clinical studies have reported many beneficial biological properties of CAP, including antioxidant, anti-inflammatory, anti-cancer, anti-obesity, cardioprotective, and circadian rhythm regulation. However, its short plasma half-life, poor water solubility, low bioavailability, and its pungent taste that causes a strong burning sensation in the mouth and stomach have adversely affected its clinical application. In order to improve the oral bioavailability of CAP and alleviate irritation to the gastrointestinal mucosa, many strategies have been developed, including liposomes, nanoemulsions, and nanoparticles. These delivery systems have multiple advantages.

First, the stability, loading capacity, and encapsulation efficiency of CAP in these preparations are high, which improves its bioacceptability and oral bioavailability.

Secondly, nano-sized capsules, particles or droplets can reduce or even eliminate the sudden release of CAP, and provide sustained release characteristics, prolonging the retention time of CAP in the digestive tract.

In addition, the use of wall materials prevents large CAP crystals from directly contacting the gastric mucosal surface, reducing irritation to the gastric mucosa.

In summary, by reviewing the biological efficacy and encapsulation methods of CAP, a theoretical basis is provided for the further development of CAP as a multifunctional food raw material with great potential in nutritional preparations.

anna@hihealthbio.com