Synthesis of Either C2- or C4'-Alkylated Derivatives of Honokiol and Their Biological Evaluation for Anti-inflammatory Activity

Recent advances of honokiol：pharmacological activities, manmade derivatives and structure-activity relationship

Honokiol (HNK) is a typical natural biphenyl polyphenol compound. It has been proven to have a wide range of biological activities, including pharmacological effects such as anti-cancer, anti-inflammatory, neuroprotective, and antimicrobial. However, due to the poor stability, water solubility, and bioavailability of HNK, HNK has not been used in clinical treatment. This article reviews the latest research on the pharmacological activity of HNK and summarizes the HNK derivatives designed and improved by several researchers. Reviewing these contents could promote the research process of HNK and guide the design of better HNK derivatives for clinical application in the future.

Non-clinical pharmacokinetics study in rat plasma, tissues and excreta of honokiol derivative HM475 by UPLC-Q-TOF-MS/MS

To provide the basis for further development and research of drugs, non-clinical pharmacokinetics studies were conducted on HM475, which is composed of natural active molecules honokiol and metformin through cyclization. In this paper, HM475 was studied from six aspects by gavage and intraperitoneal injection: 1) Acute toxicity of HM475 in rats, 2) Pharmacokinetic characteristics of HM475 in rats, 3) Distribution characteristics of HM475 in heart, liver, spleen, lung, and kidney, small intestine, fat and brain of rats, 4) Main metabolic pathways of HM475 in rats, 5) Excretion of HM475 in rats, 6) Determination of protein binding rate of HM475 in bovine plasma, rabbit plasma, and rat plasma. Acute toxicity of HM475 on SD rats was evaluated by maximum dose method. The metabolic analysis method of HM475 in rats was first established by UPLC-Q-TOF-MS/MS technology, and the pharmacokinetic characteristics of oral administration and intraperitoneal injection were studied. Experimental results showed that HM475 had no obvious acute toxicity. The absolute oral bioavailability of HM475 was 38.45 %, and the drug concentration in plasma was higher than that in tissues. Combined with the process characteristics of HM475 in vivo, it is inferred that HM475 has enterohepatic circulation. In this study, non-clinical pharmacokinetics were systematically studied to provide data support for the clinical pharmacokinetics and pharmacodynamics of HM475, to more accurately predict the pharmacokinetic behavior of HM475 in human body and provide scientific data for the compound to enter clinical research.

A small molecule compound that inhibits blue light-induced retinal damage via activation of autophagy

Dry age-related macular degeneration (AMD) is a type of disease that causes visual impairment due to changes in the macula located in the center of the retina. The accumulation of drusen under the retina is also a characteristic of dry AMD. In this study, we identified a compound (JS-017) that can potentially degrade N-retinylidene-N-retinylethanolamine (A2E), one of the components of lipofuscin, using fluorescence-based screening, which measures A2E degradation in human retinal pigment epithelial cells. JS-017 effectively degraded A2E in ARPE-19 cells and consequently suppressed the activation of the NF-κB signaling pathway and expression of inflammatory and apoptosis genes induced by blue light (BL). Mechanistically, JS-017 induced LC3-II formation and improved autophagic flux in ARPE-19 cells. Additionally, the A2E degradation activity of JS-017 was found to be decreased in autophagy-related 5 protein-depleted ARPE-19 cells, suggesting that autophagy was required for A2E degradation mediated by JS-017. Finally, JS-017 exhibited an improvement in BL-induced retinal damage measured through fundus examination in an in vivo retinal degeneration mouse model. The thickness of the outer nuclear layer and inner/external segments, which was decreased upon exposure to BL irradiation, was also restored upon JS-017 treatment. Altogether, we demonstrated that JS-017 protected human retinal pigment epithelium (RPE) cells from A2E and BL-induced damage by degrading A2E via the activation of autophagy. The results suggest the feasibility of a novel A2E-degrading small molecule as a therapeutic agent for retinal degenerative diseases.

Synergistic effect of Aloe vera flower and Aloe gel on cutaneous wound healing targeting MFAP4 and its associated signaling pathway: In-vitro study

ETHNOPHARMACOLOGICAL RELEVANCE

Aloe vera (L.) Burm. f. (Liliaceae family) is a well-known traditional medicinal plant, that has been used to treat a variety of illnesses, for decades ranging from cancer to skin disorders including wounds. It has been included in the traditional and herbal healthcare systems of many cultures around the world, as well as the pharmacopeia of different countries. Several in vitro and in vivo studies have also confirmed its potential antioxidant, anti-inflammatory, and wound-healing activities, etc. in the consistency of its historical and traditional uses. However, most studies to date are based on the A. vera gel and latex including its wound-healing effects. Very few studies have been focused on its flower, and rarely with its effects on cutaneous wound healing and its molecular mechanism.

AIM OF THE STUDY

To the best of our knowledge, this is the first study to report on the synergistic effect of the A. vera flower (AVF) and Aloe gel (PAG) on cutaneous wound-healing, as well as revealing its molecular mechanism targeting microfibril-associated glycoprotein 4 (MFAP4) and its associated signaling pathway.

METHODS

To investigate the synergistic effect of A. vera flower and Aloe gel in cutaneous wound healing, cell viability, and cell migration, as well proliferation assay was performed. This was followed by quantitative real-time polymerase chain reaction and Western blot analyses in wounded conditions to check the effects of this mixture on protein and mRNA levels in normal human dermal fibroblast (NHDF) cells. Moreover, small interfering RNA (siRNA) -mediated knockdown of MFAP4 in NHDF cells was performed followed by migration assay and cell cycle analysis, to confirm its role in cutaneous wound healing. Additionally, HaCaT cells were included in this study to evaluate its migratory and anti-inflammatory effects.

RESULTS

Based on our obtained results, the PAG and AVF mixture synergistically induced the proliferation, migration, and especially ECM formation of NHDF cells by enhancing the expression of MFAP4. Other extracellular components associated with MFAP4 signaling pathway, such as fibrillin, collagen, elastin, TGF β, and α-SMA, also increased at both the protein and mRNA levels. Subsequently, this mixture initiated the phosphorylation of the extracellular signal-regulated kinase (ERK) and AKT signaling pathways, and the S-phase of the cell cycle was also slightly modified. Also, the mixture induced the migration of HaCaT cells along with the suppression of inflammatory cytokines. Moreover, the siRNA-mediated knockdown highlighted the crucial role of MFAP4 in cutaneous wound healing in NHDF cells.

CONCLUSION

This study showed that the mixture of PAG and AVF has significant wound healing effects targeting MFAP4 and its associated signaling pathway. Additionally, MFAP4 was recognized as a new potential biomarker of wound healing, which can be confirmed by further in vivo studies.

Honokiol ameliorates angiotensin II-induced hypertension and endothelial dysfunction by inhibiting HDAC6-mediated cystathionine γ-lyase degradation

Hypertension and endothelial dysfunction are associated with various cardiovascular diseases. Hydrogen sulphide (H₂S) produced by cystathionine γ‐lyase (CSE) promotes vascular relaxation and lowers hypertension. Honokiol (HNK), a natural compound in the Magnolia plant, has been shown to retain multifunctional properties such as anti‐oxidative and anti‐inflammatory activities. However, a potential role of HNK in regulating CSE and hypertension remains largely unknown. Here, we aimed to demonstrate that HNK co‐treatment attenuated the vasoconstriction, hypertension and H₂S reduction caused by angiotensin II (AngII), a well‐established inducer of hypertension. We previously found that histone deacetylase 6 (HDAC6) mediates AngII‐induced deacetylation of CSE, which facilitates its ubiquitination and proteasomal degradation. Our current results indicated that HNK increased endothelial CSE protein levels by enhancing its stability in a sirtuin‐3‐independent manner. Notably, HNK could increase CSE acetylation levels by inhibiting HDAC6 catalytic activity, thereby blocking the AngII‐induced degradative ubiquitination of CSE. CSE acetylation and ubiquitination occurred mainly on the lysine 73 (K73) residue. Conversely, its mutant (K73R) was resistant to both acetylation and ubiquitination, exhibiting higher protein stability than that of wild‐type CSE. Collectively, our findings suggested that HNK treatment protects CSE against HDAC6‐mediated degradation and may constitute an alternative for preventing endothelial dysfunction and hypertensive disorders.

Synthesis of Bisphenol Neolignans Inspired by Honokiol as Antiproliferative Agents

Honokiol (2) is a natural bisphenol neolignan showing a variety of biological properties, including antitumor activity. Some studies pointed out 2 as a potential anticancer agent in view of its antiproliferative and pro-apoptotic activity towards tumor cells. As a further contribution to these studies, we report here the synthesis of a small library of bisphenol neolignans inspired by honokiol and the evaluation of their antiproliferative activity. The natural lead was hence subjected to simple chemical modifications to obtain the derivatives 3–9; further neolignans (12a-c, 13a-c, 14a-c, and 15a) were synthesized employing the Suzuki–Miyaura reaction, thus obtaining bisphenols with a substitution pattern different from honokiol. These compounds and the natural lead were subjected to antiproliferative assay towards HCT-116, HT-29, and PC3 tumor cell lines. Six of the neolignans show GI₅₀ values lower than those of 2 towards all cell lines. Compounds 14a, 14c, and 15a are the most effective antiproliferative agents, with GI₅₀ in the range of 3.6–19.1 µM, in some cases it is lower than those of the anticancer drug 5-fluorouracil. Flow cytometry experiments performed on these neolignans showed that the inhibition of proliferation is mainly due to an apoptotic process. These results indicate that the structural modification of honokiol may open the way to obtaining antitumor neolignans more potent than the natural lead.