Synthesis and plasma pharmacokinetics in CD-1 mice of a 18β-glycyrrhetinic acid derivative displaying anti-cancer activity

A Mini-Review on Structure-Activity Relationships of Glycyrrhetinic Acid Derivatives with Diverse Bioactivities

Pentacyclic triterpenoids, consisting of six isoprene units, are a kind of natural active substance. At present, numerous pentacyclic triterpene have been observed and classified into four subgroups of oleanane, ursane, lupane, and xylene on the basis of the carbon skeleton. Among them, oleanane is the most popular due to its rich backbone and diverse bioactivities. 18β-Glycyrrhetinic acid (GA), an oleanane-type pentacyclic triterpene isolated from licorice roots, possesses diverse bioactivities including antitumor, anti-inflammatory, antiviral, antimicrobial, enzyme inhibitor, hepatoprotective and so on. It has received more attention in medicinal chemistry due to the advantages of easy-to-access and rich bioactivity. Thus, numerous novel lead compounds were synthesized using GA as a scaffold. Herein, we summarize the structure-activity relationship and synthetic methodologies of GA derivatives from 2010 to 2020 as well as the most active GA derivatives. Finally, we anticipate that this review can benefit future research on structural modifications of GA to enhance bioactivity and provide an example for developing pentacyclic triterpene-based novel drugs.

Natural products are an important source for proteasome regulating agents

BACKGROUND

Natural medicines have a long history in the prevention and treatment of various diseases in East Asian region, especially in China. Modern research has proved that the pharmacological effects of numerous natural medicines involve the participation of ubiquitin proteasome system (UPS). UPS can degrade the unwanted and damaged proteins widely distributed in the nucleus and cytoplasm of various eukaryotes.

PURPOSE

The objective of the present study was to review and discuss the regulatory effects of natural products and extracts on proteasome components, which may help to find new proteasome regulators for drug development and clinical applications.

METHODS

The related information was compiled using the major scientific databases, such as CNKI, Elsevier, ScienceDirect, PubMed, SpringerLink, Wiley Online, and GeenMedical. The keywords "natural product" and "proteasome" were applied to extract the literature. Nature derived extracts, compounds and their derivatives involved in proteasome regulation were included, and the publications related to synthetic proteasome agents were excluded.

RESULTS

The pharmacological effects of more than 80 natural products and extracts derived from phytomedicines related to the proteasome regulation were reviewed. These natural products were classified according to their chemical properties. We also summarized some laws of action of natural products as proteasome regulators in the treatment of diseases, and listed the action characteristics of the typical natural products.

CONCLUSION

Natural products derived from nature can induce the degradation of damaged proteins through UPS or act as regulators to directly regulate the activity of proteasome. But few proteasome modulators are applied clinically. Summary of known rules for proteasome modulators will contribute to discover, modify and synthesize more proteasome modulators for clinical applications.

Recent Advances in the Design of Topical Ophthalmic Delivery Systems in the Treatment of Ocular Surface Inflammation and Their Biopharmaceutical Evaluation

Ocular inflammation is one of the most common symptom of eye disorders and diseases. The therapeutic management of this inflammation must be rapid and effective in order to avoid deleterious effects for the eye and the vision. Steroidal (SAID) and non-steroidal (NSAID) anti-inflammatory drugs and immunosuppressive agents have been shown to be effective in treating inflammation of the ocular surface of the eye by topical administration. However, it is well established that the anatomical and physiological ocular barriers are limiting factors for drug penetration. In addition, such drugs are generally characterized by a very low aqueous solubility, resulting in low bioavailability as only 1% to 5% of the applied drug permeates the cornea. The present review gives an updated insight on the conventional formulations used in the treatment of ocular inflammation, i.e., ointments, eye drops, solutions, suspensions, gels, and emulsions, based on the commercial products available on the US, European, and French markets. Additionally, sophisticated formulations and innovative ocular drug delivery systems will be discussed. Promising results are presented with micro- and nanoparticulated systems, or combined strategies with polymers and colloidal systems, which offer a synergy in bioavailability and sustained release. Finally, different tools allowing the physical characterization of all these delivery systems, as well as in vitro, ex vivo, and in vivo evaluations, will be considered with regards to the safety, the tolerance, and the efficiency of the drug products.

18β-Glycyrrhetinic acid mitigates radiation-induced skin damage via NADPH oxidase/ROS/p38MAPK and NF-κB pathways

Radiation-induced inflammation plays an important role in radiation-induced tissue injury. 18β-glycyrrhetinic acid (18β-GA) has shown an anti-inflammatory activity. This study aimed to assess the activity of 18β-GA against radiation-induced skin damage, and explore the underlying mechanisms. In vitro assay revealed 18β-GA treatment decreased the production of IL-1β, IL-6, PGE2 and decreased p38MAPK phosphorylation, DNA-binding activity of AP-1, and NF-κB activation in irradiated RAW264.7 macrophages. Additionally, 18β-GA suppressed NF-κB activation by inhibiting NF-κB/p65 and IκB-α phosphorylation and alleviated ROS overproduction in irradiated RAW264.7 macrophages. In vivo assay showed 18β-GA alleviated severity of radiation-induced skin damage, reduced inflammatory cell infiltration and TNF-α, IL-1β and IL-6 levels in cutaneous tissues. Our findings demonstrate that 18β-GA exhibits anti-inflammatory actions against radiation-induced skin damage probably by inhibiting NADPH oxidase activity, ROS production, activation of p38MAPK and NF-κB signaling, and the DNA binding activities of NF-κB and AP-1, consequently suppressing pro-inflammatory cytokine production.

18β-Glycyrrhetinic acid suppresses cell proliferation through inhibiting thromboxane synthase in non-small cell lung cancer

18β-glycyrrhetinic acid (18β-GA) is a bioactive component of licorice. The anti-cancer activity of 18β-GA has been studied in many cancer types, whereas its effects in lung cancer remain largely unknown. We first showed that 18β-GA effectively suppressed cell proliferation and inhibited expression as well as activity of thromboxane synthase (TxAS) in non-small cell lung cancer (NSCLC) cells A549 and NCI-H460. In addition, the administration of 18β-GA did not have any additional inhibitory effect on the decrease of cell proliferation induced by transfection with TxAS small interference RNA (siRNA). Moreover, 18β-GA failed to inhibit cell proliferation in the immortalized human bronchial epithelial cells 16HBE-T and another NSCLC cell line NCI-H23, both of which expressed minimal level of TxAS as compared to A549 and NCI-H460. However, 18β-GA abolished the enhancement of cell proliferation induced by transfection of NCI-H23 with pCMV6-TxAS plasmid. Further study found that the activation of both extracellular signal-regulated kinase (ERK)1/2 and cyclic adenosine monophosphate response element binding protein (CREB) induced by TxAS cDNA transfection could be totally blocked by 18β-GA. Altogether, we have delineated that, through inhibiting TxAS and its initiated ERK/CREB signaling, 18β-GA suppresses NSCLC cell proliferation. Our study has highlighted the significance of 18β-GA with respect to prevention and treatment of NSCLC.