Phenolic Profile and Fingerprint Analysis of Akebia quinata Leaves Extract with Endothelial Protective Activity

In contrast to the stem and fruit of Akebia quinata, A. quinata leaves as a source rich in phenolic compounds with potentially beneficial pharmacological activities have been largely overlooked. To develop and use A. quinata leaves as a resource, we evaluated its potential as a cardiovascular-protective agent. Herein, we investigated the effects and potential mechanisms of A. quinata leaves extract on lipopolysaccharide (LPS)-induced inflammatory responses in human umbilical vein endothelial cells. We found that A. quinata leaves extract pretreatment of 10 μg/mL significantly attenuated LPS-induced protein expression of intercellular adhesion molecule-1, vascular cell adhesion molecule-1. Furthermore, this extract also suppressed LPS-induced phosphorylation of nuclear factor-κB p65. In order to elucidate the chemical profiles of the samples, the HPLC fingerprint was established, and prominent peaks were identified via HPLC–electrospray ionization–mass spectrometry. Multivariate statistical analyses, including hierarchical cluster analysis, principal component analysis, and partial least-squares discriminant analysis, were performed to evaluate the clustering of the samples. It was found that isochlorogenic acid C was a key marker for the classification of A. quinata leaves from the Gongju and Muju city in Korea. Collectively, this study not only suggested the potential of A. quinata leaves as a novel therapeutic candidate for inflammatory cardiovascular disease but also developed a quality control method for A. quinata leaves, which could help to expand the application of A. quinata.

Akebia quinata and Akebia trifoliata - a review of phytochemical composition, ethnopharmacological approaches and biological studies

ETHNOPHARMACOLOGICAL RELEVANCE

'Akebia stem' (Akebiae caulis) is one of the newest raw materials officially introduced into therapeutic practice from traditional Chinese medicine. A monograph on this material appeared for the first time in 2018 in Supplement 9.6 to the 9th edition of the European Pharmacopoeia. In the latest 10th edition of the European Pharmacopoeia, the monograph remained unchanged. The 'Akebia stem' monograph allows the use, as a raw material, of Akebia quinata (Houtt.) Decne., A. trifoliata (Thunb.) Koidz, or a mixture of the two species.

AIM OF THE STUDY

The aim of this work is a detailed review of the scientific literature on the genus Akebia (family Lardizabalaceae), with particular emphasis on A. quinata and A. trifoliata, providing information on the botanical, ecological, and chemical characteristics of these species. Professional research on their biological activity has been reviewed. The attention is given to phytochemistry and cosmetology. The traditional use of Akebia species and their potential use in medicine and cosmetology are assessed. In addition, individual papers describing biotechnology research on in vitro cultures of the two Akebia species are presented.

MATERIALS AND METHODS

The presented botanical, ecological, phytochemical and biotechnological characterization is based on a thorough review of published scientific research. It is a compilation and evaluation of data on the chemical composition and biological activities of these Akebia species.

RESULTS

This critical review of phytochemical studies demonstrates that triterpenoid saponins are dominant secondary metabolites of these species. A comparative analysis of phytochemical studies on A. quinata and A. trifoliata stems, roots, fruits, and seeds showed differences in metabolites based on the plant parts and species. The triterpenoid saponins mutongsaponin C and saponin P_j1 have been found only in A. trifoliata, whereas the phenolic glycoside 2-(3,4-dihydroxyphenyl)-ethyl-O-β-D-glucopyranoside has been found only in A. quinata. Biological activity studies of A. quinata stem, leaf and/or fruit extracts have confirmed diuretic, hepatoregenerative, neuroprotective, analgesic, anti-inflammatory, and anti-obesity effects and an influence on ethanol metabolism. Different action profiles have been demonstrated for A. trifoliata stem, leaf and/or fruit extracts. Studies have proven the antibacterial and anticancer (liver and stomach) effects of these species. This review presents potential phytopharmacological applications of both species and detailed data on their broad applications in cosmetology. Attention is also drawn to information on the safety of using Akebia. Finally, an overview of biotechnology research on both species is presented.

CONCLUSIONS

This review provides comprehensive knowledge about the ethnopharmacological use of Akebia species. Moreover, new findings on the differences in the chemical composition and biological activity profiles are underlined.

Traditional uses, phytochemistry, pharmacology, and toxicology of Akebiae Caulis and its synonyms: A review

ETHNOPHARMACOLOGICAL RELEVANCE

"Mutong" ( in Chinese, and generally known as Akebiae Caulis), which refers to a group of herbal medicines with different biological origins along history, has been used in traditional Chinese medicine for over 2000 years; it is still being frequently used in medicine. In recent decades, Akebiae Caulis has been reported to exhibit apparent toxicity.

AIM OF THIS STUDY

To clarify the plant species used as Akebiae Caulis and its synonyms, and to summarize their phytochemistry, pharmacology, and toxicology.

METHODS

Academic search engines (Google Scholar, Baidu Scholar, CNKI, Science Direct, Springer Link, SciFinder, PubMed, Web of Science, and EBSCO), ancient Chinese herbals, and modern medical monographs were used to obtain phytochemical, pharmacological, toxicological, and quality control information. Furthermore, a field survey was conducted to clarify the associated species.

RESULTS

Akebiae Caulis is derived from eight species belonging to two families. In the 2005 Pharmacopoeia of The People's Republic of China, it has been separated into two categories: Akebiae Caulis and Clematidis Armandii Caulis. Traditionally, Akebiae Caulis has been used to treat conditions such as gonorrhea, edema, and tongue sores. Pharmacological studies have demonstrated the anti-inflammatory, antitumor, antihypertensive, antibacterial, analgesic, and other properties of Akebiae Caulis. Among the species used, Aristolochiae manshuriensis Kom. (Aristolochiaceae) contains aristolochic acid that has raised concerns globally because of its nephrotoxicity.

CONCLUSIONS

Clarifying the biological origin of traditional herbal medicines is critical for their safe and effective use. The present review revealed that the biological origin of Akebiae Caulis is diverse. The traditional uses, phytochemistry, and pharmacology of Akebiae Caulis indicate that it is a useful medical resource. The diversity of its biological and pharmacological activities is associated with the presence of a large number of chemical substances, among which terpenoids are predominant. Systematic reviews on Akebiae Caulis such as this one would provide solid references for its safe use, as well as drug discovery studies in the future.

Polyphenolic compounds as electron shuttles for sustainable energy utilization

For renewable and sustainable bioenergy utilization with cost-effectiveness, electron-shuttles (ESs) (or redox mediators (RMs)) act as electrochemical "catalysts" to enhance rates of redox reactions, catalytically accelerating electron transport efficiency for abiotic and biotic electrochemical reactions. ESs are popularly used in cellular respiratory systems, metabolisms in organisms, and widely applied to support global lives. Apparently, they are applicable to increase power-generating capabilities for energy utilization and/or fuel storage (i.e., dye-sensitized solar cell, batteries, and microbial fuel cells (MFCs)). This first-attempt review specifically deciphers the chemical structure association with characteristics of ESs, and discloses redox-mediating potentials of polyphenolics-abundant ESs via MFC modules. Moreover, to effectively convert electron-shuttling capabilities from non-sustainable antioxidant activities, environmental conditions to induce electrochemical mediation apparently play critical roles of great significance for bioenergy stimulation. For example, pH levels would significantly affect electrochemical potentials to be exhibited (e.g., alkaline pHs are electrochemically favorable for expression of such electron-shuttling characteristics). Regarding chemical structure effect, chemicals with ortho- and para-dihydroxyl substituents-bearing aromatics own convertible characteristics of non-renewable antioxidants and electrochemically catalytic ESs; however, ES capabilities of meta-dihydroxyl substituents can be evidently repressed due to lack of resonance effect in the structure for intermediate radical(s) during redox reaction. Moreover, this review provides conclusive remarks to elucidate the promising feasibility to identify whether such characteristics are non-renewable antioxidants or reversible ESs from natural polyphenols via cyclic voltammetry and MFC evaluation. Evidently, considering sustainable development, such electrochemically convertible polyphenolic species in plant extracts can be reversibly expressed for bioenergy-stimulating capabilities in MFCs under electrochemically favorable conditions.