A Behavioral Survey of the Effects of Kavalactones on Caenorhabditis elegans Neuromuscular Transmission

Yangonin, one of the kavalactones isolated from Piper methysticum G. Forst, acts through cannabinoid 1 (CB1) receptors to induce an intrathecal anti-hyperalgesia

ETHNOPHARMACOLOGICAL RELEVANCE

Piper methysticum G. Forst (Piperaceae) is traditionally consumed in Polynesian culture. The roots are used to produce an entheogenic drink and traditional medicine with sedative and anxiolytic properties. There is also evidence that it functions as a pain reliever. Kavalactones, its main active ingredients, exhibit psychoactive effects on the central nervous system. However, the active ingredients and pharmacological mechanisms underlying the analgesic effect of kavalactones are unclear.

AIM OF THE STUDY

This study investigated the effects of kavain and yangonin on nociception, inflammatory hyperalgesia, and neuropathic mechanical allodynia at the spinal level.

MATERIALS AND METHODS

Male Sprague-Dawley rats were administered kavain and yangonin (27.14 and 19.36 nmol/rat) via intrathecal injection. Tail-flick tests were performed to evaluate the anti-nociceptive properties. The efficacy of kavain and yangonin on inflammatory hyperalgesia was examined using a plantar test in rats with carrageenan-induced paw inflammation. The von Frey test was used to assess mechanical allodynia induced by partial sciatic nerve ligation.

RESULTS

Intrathecal injection of yangonin demonstrated a relatively potent anti-nociceptive effect and attenuated carrageenan-induced hyperalgesia. These effects were completely reversed by the co-administration of PF 514273, a cannabinoid 1 (CB1) receptor antagonist. However, yangonin did not affect mechanical allodynia at the spinal level. Kavain, another abundant kavalactone, did not affect nociception, hyperalgesia, or mechanical allodynia at the spinal level.

CONCLUSIONS

Overall, our study demonstrated that yangonin exerts anti-nociception and anti-inflammatory hyperalgesia effects via CB1 receptors at the spinal level. We identified a single kavalactone, yangonin, extracted from kava as a promising treatment for pain.

Screening tools to evaluate the neurotoxic potential of botanicals: building a strategy to assess safety

AREAS COVERED

This paper outlines the selection of NAMs, including in vitro assays using primary rat cortical neurons, zebrafish embryos, and Caenorhabditis elegans. These assays aim to assess neurotoxic endpoints such as neuronal activity and behavioral responses. Microelectrode array recordings of rat cortical neurons provide insights into the impact of botanical extracts on neuronal function, while the zebrafish embryos and C. elegans assays evaluate neurobehavioral responses. The paper also provides an account of the selection of botanical case studies based on expert judgment and existing neuroactivity/toxicity information. The proposed battery of assays will be tested with these case studies to evaluate their utility for neurotoxicity screening.

EXPERT OPINION

The complexity of botanicals necessitates the use of multiple NAMs for effective neurotoxicity screening. This paper discusses the evaluation of methodologies to develop a robust framework for evaluating botanical safety, including complex neuronal models and key neurodevelopmental process assays. It aims to establish a comprehensive screening framework.

Construction of an Artificial Biosynthetic Pathway for the Styrylpyrone Compound 11-Methoxy-Bisnoryangonin Produced in Engineered Escherichia coli

A cDNA clone (named pnpks), which shows high homology to the known chalcone synthase (CHS)-like type III PKS, was obtained from the leaves of Piper nigrum. The PnPKS protein with ferulic acid catalyzed lactonization instead of chalcone or stilbene formation. The new product was characterized as a styrylpyrone, 11-methoxy-bisnoryangonin, which is the lactonization compound of a linear triketide formed as the reaction product of PnPKS protein with ferulic acid. These results show that pnpks encodes a styrylpyrone synthase (SPS)-like PKS that catalyzes two-chain elongation with feruloyl CoA-linked starter substrates. Although these styrylpyrone compounds are promising for use in human healthcare, they are mainly obtained by extraction from raw plant or mushroom sources. For de novo synthesis of 11-methoxy-bisnoryangonin in the heterologous host Escherichia coli from a simple sugar as a starter, the artificial biosynthetic pathway contained five genes: optal, sam5, com, and 4cl2nt, along with the pnpks gene. The engineered _L-tyrosine overproducing E. coli ∆COS1 strain, in which five biosynthetic genes were cloned into two vectors, pET-opT5M and pET22-4P, was cultured for 24 h in a minimal glucose medium containing ampicillin and kanamycin. As a result, 11-methoxy-bisnoryangonin production of up to 52.8 mg/L was achieved, which is approximately 8.5-fold higher than that in the parental E. coli strain harboring a plasmid for 11-methoxy-bisnoryangonin biosynthesis. As a potential styrylpyrone compound, 11-methoxy-bisnoryangonin, was successfully produced in E. coli from a simple glucose medium, and its production titer was also increased using engineered strains. This study provides a useful reference for establishing the biological manufacture of styrylpyrone compounds.

The Pharmacology, Pharmacokinetics, Efficacy, and Adverse Events Associated With Kava

Kava is a plant with numerous kavapyrones that can induce pharmacologic effects and drug interactions through the cytochrome P450 and P-glycoprotein systems. Kava is used recreationally and for the treatment of anxiety. Clinical trials verify anxiolytic effects in excess of placebo, but the effects are not seen immediately and the optimal dose and dosing schedule needs to be determined. Clinical trials usually lasting for 4 weeks found generally good tolerability and safety; however, dermatologic, hepatologic, and cognitive adverse effects may occur. Some of these adverse effects are known to occur from the kavapyrones themselves, while others can be caused or exacerbated by use of substandard kava products. There is tremendous variability in the constitution of a kava product based on the parts of the plant that are being extracted and the extraction method. The most commonly studied extract for the treatment of anxiety is the acetone extract.