Synthesis and structure-activity relationship of 8-substituted protoberberine derivatives as a novel class of antitubercular agents

Alkaloids of Dicranostigma franchetianum (Papaveraceae) and Berberine Derivatives as a New Class of Antimycobacterial Agents

Tuberculosis (TB) is a widespread infectious disease caused by Mycobacterium tuberculosis. The increasing incidence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains has created a need for new antiTB agents with new chemical scaffolds to combat the disease. Thus, the key question is: how to search for new antiTB and where to look for them? One of the possibilities is to search among natural products (NPs). In order to search for new antiTB drugs, the detailed phytochemical study of the whole Dicranostigma franchetianum plant was performed isolating wide spectrum of isoquinoline alkaloids (IAs). The chemical structures of the isolated alkaloids were determined by a combination of MS, HRMS, 1D, and 2D NMR techniques, and by comparison with literature data. Alkaloids were screened against Mycobacterium tuberculosis H37Ra and four other mycobacterial strains (M. aurum, M. avium, M. kansasii, and M. smegmatis). Alkaloids 3 and 5 showed moderate antimycobacterial activity against all tested strains (MICs 15.625–31.25 µg/mL). Furthermore, ten semisynthetic berberine (16a–16k) derivatives were developed and tested for antimycobacterial activity. In general, the derivatization of berberine was connected with a significant increase in antimycobacterial activity against all tested strains (MICs 0.39–7.81 μg/mL). Two derivatives (16e, 16k) were identified as compounds with micromolar MICs against M. tuberculosis H37Ra (MIC 2.96 and 2.78 µM). All compounds were also evaluated for their in vitro hepatotoxicity on a hepatocellular carcinoma cell line (HepG2), exerting lower cytotoxicity profile than their MIC values, thereby potentially reaching an effective concentration without revealing toxic side effects.

Synthesis of 9-O-arylated berberines via copper-catalyzed CAr-O coupling reactions

Berberine is a widely used antimicrobial agent in clinic. However, a high dosage is often required due to its low lipophilicity and bioavailability. The current study explores the structural modifications of berberines with potentially lipophilic aryl groups to address this problem. A series of 15 9-O-aryl-substituted berberines (3a–o) and one 9-O-phenylene-bridged berberine dimer (5) was synthesized by copper-catalyzed cross-coupling of tetrahydroberberrubine and aryl iodides, followed by oxidation with I₂.

Novel berberine derivatives: Design, synthesis, antimicrobial effects, and molecular docking studies

A series of berberine derivatives were synthesized by introducing substituted benzyl groups at C-9. All these synthesized compounds (4a-4m) were screened for their in vitro antibacterial activity against four Gram-positive bacteria and four Gram-negative bacteria and evaluated for their antifungal activity against three pathogenic fungal strains. All these compounds displayed good antibacterial and antifungal activities, compared to reference drugs including Ciprofloxacin and Fluconazole; Compounds 4f, 4g, and 4l showed the highest antibacterial and antifungal activities. Moreover, all the synthesized compounds were docked into topoisomerase II-DNA complex, which is a crucial drug target for the treatment of microbial infections. Docking results showed that H-bond, π-π stacked, π-cationic, and π-anionic interactions were responsible for the strong binding of the compounds with the target protein-DNA complex.

Synthesis and antibacterial evaluation of 13-substituted cycloberberine derivatives as a novel class of anti-MRSA agents

A series of new 13-substituted cycloberberine (CBBR) derivatives were prepared and evaluated for their antibacterial activities against Gram-positive bacteria taking CBBR as the lead. Structure-activity relationship revealed that the introduction of a suitable electron-donating group at the 13-position in CBBR might be beneficial for the antibacterial potency. Among them, compounds 5b and 5w exhibited high potency against methicillin-sensitive (MSSA) and resistant strains of S. aureus (MRSA) with MIC values of 1-4 μg/mL. Both of them also displayed high stabilities in blood, and good in vivo safety profiles with LD₅₀ values of 65.6 and 41.2 mg kg^-1 in intravenous route respectively. Molecular docking analysis indicated that compound 5b might target FtsZ protein that could inhibit cell division, with the advantage of activity against multidrug resistant S. aureus. Therefore, we consider 13-substituted CBBR derivatives to be a novel class of anti-MRSA agents worthy of further investigation.

Chemical composition and in vitro evaluation of the cytotoxic and antioxidant activities of supercritical carbon dioxide extracts of pitaya (dragon fruit) peel

Background

Hylocereus polyrhizus and Hylocereus undatus are two varieties of the commonly called pitaya fruits, and pitaya fruits have gained popularity in many countries all over the world. However, studies on chemical composition and the nutritional quality of pitaya flesh peel are limited.

Results

Extracts of pitaya (H. polyrhizus and H. undatus) peel were extracted by supercritical carbon dioxide extraction, and analyzed by gas chromatography–mass spectrometry analysis. Their cytotoxic and antioxidant activities were investigated. The main components of H. polyrhizus extract were β-amyrin (15.87%), α-amyrin (13.90%), octacosane (12.2%), γ-sitosterol (9.35%), octadecane (6.27%), 1-tetracosanol (5.19%), stigmast-4-en-3-one (4.65%), and campesterol (4.16%), whereas H. undatus were β-amyrin (23.39%), γ-sitosterol (19.32%), and octadecane (9.25%), heptacosane (5.52%), campesterol (5.27%), nonacosane (5.02%), and trichloroacetic acid, hexadecyl ester (5.21%). Both of the two extracts possessed good cytotoxic activities against PC3, Bcap-37, and MGC-803 cells (IC₅₀ values ranging from 0.61 to 0.73 mg/mL), and the activities of their main components were also studied. Furthermore, these extracts also presented some radical scavenging activities, with IC₅₀ values of 0.83 and 0.91 mg/mL, respectively.

Conclusion

This paper provides evidence for studying the chemical composition of supercritical carbon dioxide extracts of pitaya peel and their biological activity.