Design, Synthesis, and In Vitro and In Vivo Biological Evaluation of Limonin Derivatives for Anti-Inflammation Therapy

Design, synthesis, in vitro and in vivo biological evaluation of pterostilbene derivatives for anti-inflammation therapy

Pterostilbene (PST) is a naturally derived stilbene compound in grapes, blueberries, and other fruits. It is also a natural dietary compound with a wide range of biological activities such as antioxidant, anti-inflammatory, antitumor, and so on. Structural modifications based on the chemical scaffold of the pterostilbene skeleton are of great importance for drug discovery. In this study, pterostilbene skeletons were used to design novel anti-inflammatory compounds with high activity and low toxicity. A total of 30 new were found and synthesised, and their anti-inflammatory activity and safety were screened. Among them, compound E2 was the most active (against NO: IC50 = 0.7 μM) than celecoxib. Further studies showed that compound E2 exerted anti-inflammatory activity by blocking LPS-induced NF-κB/MAPK signalling pathway activation. In vivo experiments revealed that compound E2 had a good alleviating effect on acute colitis in mice. In conclusion, compound E2 may be a promising anti-inflammatory lead compound.

Limonin (LM) and its derivatives: Unveiling the neuroprotective and anti-inflammatory potential of LM and V-A-4 in the management of Alzheimer's disease and Parkinson's disease

Neuroinflammation and neuronal apoptosis are central pathogenic consequences associated with Alzheimer's Disease (AD) and Parkinson's Disease (PD). Limonin (LM), a tetracyclic triterpenoid available in citrus fruits, has anti-tumor, antioxidant, anti-inflammatory, hepatoprotective, and neuroprotective actions. LM derivative, V-A-4 emerged as a potential neuroprotective drug due to their ability to target multiple molecular pathways intertwined with neuroinflammation and neuronal apoptosis. To date, the treatment of AD and PD is not successful even though the understanding of the mechanism of neuroinflammation and neuronal apoptosis is vast in the literature. Thus, there is an urgent need to identify novel neuroprotective drugs that could target the multiple molecular pathways associated with neuroinflammation and neuronal apoptosis. The various online databases (Google scholar, Pubmed, Scopus) were searched via keywords: limonin, limonin derivatives and neuroprotection. This review highlights the multifunctional nature of LM and derivatives in combating neuroinflammation and neuronal apoptosis by stimulating PI3K/AKT and downregulating TLR4/NF-κB critical pathways. By intervening in the secretion of NO and TNF-α from glial cells, V-A-4 attenuates the damaging cascade of neuroinflammation by suppressing IKK-α and IKK-β. Furthermore, V-A-4 demonstrates its versatility by suppressing the manifestation of miR-146a and miR-155, both intimately linked to neuroinflammation, this review summarized the activities of LM and its derivatives against AD and PD, with a special focus on V-A-4 as an effective neuroprotective drug. V-A-4's ability to stimulate PI3K/AKT signaling further underscores its neuroprotective effect in combating AD and PD. More in-vitro cell line studies are needed to develop V-A-4 as an upcoming neuroprotective compound.

Design, synthesis and evaluation of ursodeoxycholic acid-cinnamic acid hybrids as potential anti-inflammatory agents by inhibiting Akt/NF-κB and MAPK signaling pathways

A series of ursodeoxycholic acid (UDCA)-cinnamic acid hybrids were designed and synthesized. The anti-inflammatory activity of these derivatives was screened through evaluating their inhibitory effects of LPS-induced nitric oxide production in RAW264.7 macrophages. The preliminary structure-activity relationship was concluded. Among them, 2m showed the best inhibitory activity against NO (IC50 = 7.70 μM) with no significant toxicity. Further study revealed that 2m significantly decreased the levels of TNF-α, IL-1β, IL-6 and PGE2, down-regulated the expression of iNOS and COX-2. Preliminary mechanism study indicated that the anti-inflammatory activity of 2m was related to the inhibition of the Akt/NF-κB and MAPK signaling pathway. Furthermore, 2m reduced inflammation by a mouse model of LPS-induced inflammatory disease in vivo. In brief, our findings indicated that 2m might serve as a new lead compound for further development of anti-inflammatory agents.

Design, synthesis fusidic acid derivatives alleviate acute lung injury via inhibiting MAPK/NF-κB/NLRP3 pathway

Acute lung injury (ALI) refers to a series of lung lesions resulting from multiple lung injuries, even leading to morbidity and death, abundant previous reports have showed that anti-inflammatory as a key to treatment of ALI. Fusidic acid (FA) as an antibiotic has significant anti-bacterial activity and anti-inflammatory effects. In this study, we designed and synthesized 34 FA derivatives to identify new anti-inflammatory drugs. The anti-inflammatory activities of the derivatives were screened using lipopolysaccharide (LPS)-induced RAW264.7 cells to evaluate the anti-inflammatory activity of the compounds, we measured nitric oxide (NO) and interleukin-6 (IL-6). Most of compounds showed inhibitory effects on inflammatory NO and IL-6 in LPS-induced RAW264.7 cells. Based on the screening results, compound a1 showed the strongest anti-inflammatory activity. Compared with FA, the inhibition rate NO and IL-6 of compound a1 increased 3.08 and 2.09 times at 10 μM, respectively. We further measured a1 inhibited inflammatory factor NO (IC50 = 3.26 ± 0.42 μM), IL-6 (IC50 = 1.85 ± 0.21 μM) and TNF-α (IC50 = 3.88 ± 0.55 μM). We also demonstrated that a1 markedly inhibits the expression of certain immune-related cytotoxic factors, including cyclooxygenase-2 (COX-2) and inducible nitric-oxide synthase (iNOS). In vivo results indicate that a1 can reduce lung inflammation and NO, IL-6, TNF-α, COX-2 and iNOS in LPS-induced ALI mice. On the one hand, we demonstrated a1 inhibits the mitogen-activated protein kinase (MAPK) signaling pathway by down-regulating the phosphorylation of p38 MAPK, c-Jun N-terminal kinase (c-JNK) and extracellular signal-regulated kinase (ERK). Moreover, a1 also suppressing the phosphorylation of inhibitory NF-κB inhibitor α (IκBα) inhibits the activation of the nuclear factor-κB (NF-κB) signaling pathway. On the other hand, we demonstrated a1 also role in anti-inflammatory by inhibits nucleotide-binding domain (NOD)-like receptor protein 3 (NLRP3) inflammasome and further inhibits Caspase-1 and inflammatory factor interleukin-1β (IL-1β). In conclusion, our study demonstrates that a1 has an anti-inflammatory effect and alleviates ALI by regulating inflammatory mediators and suppressing the MAPK, NF-κB and NLRP3 inflammasome signaling pathways.

An overview of limonoid synthetic derivatives as promising bioactive molecules

Limonoids, a class of abundant natural tetracyclic triterpenoids, present diverse biological activity and provide a versatile platform amenable by chemical modifications for clinical use. Among all of the limonoids isolated from natural sources, obacunone, nomilin, and limonin are the primary hub of limonoid-based chemical modification research. To date, more than 800 limonoids analogs have been synthesized, some of which possess promising biological activities. This review not only discusses the synthesis of limonoid derivatives as promising therapeutic candidates and details the pharmacological studies of their underlying mechanisms from 2002 to 2022, but also proposes a preliminary limonoid synthetic structure-activity relationship (SAR) and provides future direction of limonoid derivatization research.

Application of cinnamic acid in the structural modification of natural products: A review

Natural products can generally exhibit a variety of biological activities, but most show mediocre performance in preliminary activity evaluation. Natural products often require structural modification to obtain promising lead compounds. Cinnamic acid (CA) is readily available and has diverse biological activities and low cytotoxicity. Introducing CA into natural products may improve their performance, enhance biological activity, and reduce toxic side effect. Herein, we aimed to discuss related applications of CA in the structural modification of natural products and provide a theoretical basis for future derivatization and drug development of natural products. Published articles, web databases (PubMed, Science Direct, SCI Finder, and CNKI), and clinical trial websites (https://clinicaltrials.gov/) related to natural products and CA derivatives were included in the discussion. Based on the inclusion criteria, 128 studies were selected and discussed herein. Screening natural products of CA derivatives allowed for classification by their biological activities. The full text is organized according to the biological activities of the derivatives, with the following categories: anti-tumor, neuroprotective, anti-diabetic, anti-microbial, anti-parasitic, anti-oxidative, anti-inflammatory, and other activities. The biological activity of each CA derivative is discussed in detail. Notably, most derivatives exhibited enhanced biological activity and reduced cytotoxicity compared with the lead compound. CA has various advantages and can be widely used in the synthesis of natural product derivatives to enhance the properties of drug candidates or lead compounds.