Synthesis and Biological Evaluation of Strictosamide Derivatives with Improved Antiviral and Antiproliferative Activities

Nauclea officinalis: A Chinese medicinal herb with phytochemical, biological, and pharmacological effects

Nauclea officinalis (N. officinalis), a medicinal plant of the genus Nauclea in the family Rubiaceae, is used in the treatment of fever, pneumonia, pharyngolaryngitis, and enteritis in China. Extracts of N. officinalis include alkaloids, phenolic acids, pentacyclic triterpenoids, and flavonoids, which exert all kinds of pharmacological effects, for instance anti-inflammatory, anti-tumor, antibacterial, and antiviral and therefore show good effectiveness. To gain a comprehensive and deep understanding, the medicinal chemistry and chemical biology of N. officinalis are summarized in this review to provide a theoretical basis. The pharmacological effects were reviewed to provide evidence or insights into potential opportunities for further studies and medicinal exploitation of N. officinalis.

Strictosamide alleviates the inflammation in an acute ulcerative colitis (UC) model

The ulcerative colitis (UC) is a typical inflammatory bowel disease (IBD) causing great damages, while strictosamide (STR) is a natural alkaloid that possesses strong anti-inflammatory property in infection and inflammation-related diseases. Our study is aimed at evaluating the anti-inflammatory activity of STR in the course of UC. Briefly, male Balb/c mice were treated with 3.5% dextran sulfate sodium (DSS) for 6 consecutive days to establish an acute model of UC, and the administration of gradient concentrations of STR was subsequently performed. Accordingly, colonic pathological alterations including the reduced ratio of colon weight/length, decreased disease activity index (DAI), and attenuated H&E damage were found in UC mice after STR treatment. Based on the analyses of real-time PCR and western blot, downregulation of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) was also determined in the colonic tissue of UC mice after the treatment of STR. ELISA and immunohistochemical staining further suggest the relief of inflammation in UC mice with decreased expressions of MPO and iNOS after STR treatment. In addition, STR was also validated to significantly inhibit NF-κB signaling in UC mice by western blot and Electrophoretic Mobility Shift Assay (EMSA). Meanwhile, restricted inflammation was also determined in STR-treated IEC6 and HT-29 cells. The utilization of PDTC, an inhibitor of NF-κB, further demonstrated that STR ameliorated the inflammation by inhibiting the NF-κB signaling in vitro. In summary, our study suggests that STR could be a potential candidate for IBD therapy.

Chromatographic fingerprints analysis and determination of seven components in Danmu preparations by HPLC-DAD/QTOF-MS

Background

Danmu preparations (Danmu Capsule and Danmu Syrup), which are made from Nauclea officinalis stem extracts, have good clinical efficacy in acute tonsillitis, acute pharyngitis and upper respiratory tract infection. However, there is currently no reliable and systematic method to control the quality of these two Danmu preparations.

Methods

Using high-performance liquid chromatography (HPLC) coupled with diode array detection (DAD), the fingerprints of the Danmu preparations were established at 250 nm to comprehensively investigate the stability of preparation process. The chemical constituents in the Danmu preparations were separated and identified by HPLC coupled with quadrupole-time-of-flight high-definition mass spectrometry (HPLC–Q-TOF-MS). And seven major components were simultaneously determined at dual wavelengths (250 nm, 326 nm).

Results

The results of HPLC fingerprint similarity evaluation showed that the similarity values of 25 batches of Danmu preparations were more than 0.993. Twenty-three compounds, including 10 alkaloids, 6 phenolic acids, 2 iridoids, and 5 unknown compounds, were identified or tentatively characterized according to the retention times and MS/MS fragment patterns of compounds. The developed assay method of seven components was validated with acceptable linearity, precision, repeatability, stability and recovery. The contents of strictosamide belonging to alkaloids as the most abundant constituent in Danmu Capsule and Danmu Syrup were 43,681.20–99,652.49 μg/g and 1567.83–2427.25 μg/mL respectively. The contents of protocatechuic acid which were the highest in measured phenolic acids were 2633.01–7739.78 μg/g in Danmu Capsule and 192.05–448.71 μg/mL in Danmu Syrup, respectively. As an iridoid, the contents of sweroside in Danmu Capsule and Danmu Syrup were 1573.82–2789.81 μg/g and 70.32–182.81 μg/mL, respectively.

Conclusion

The established qualitative analysis method of fingerprint can be used to attain standardization, uniformity and stability of the preparation process. Meanwhile, the quantitative analysis in this study can be used as an accurate assay method for preparations.

Traditional uses, phytochemistry and pharmacological properties of African Nauclea species: A review

ETHNOPHARMACOALOGICAL RELEVANCE

The genus Nauclea in Africa comprises seven species. Among them, N. latifolia, N. diderrichii and N. pobeguinii are widely used by the local population in traditional remedies. Preparation from various parts of plants (e.g. roots, bark, leaves) are indicated by traditional healers for a wide range of diseases including malaria, pain, digestive ailments or metabolic diseases.

MATERIALS AND METHODS

A literature search was conducted on African species of the genus Nauclea using scientific databases such as Google Scholar, Pubmed or SciFinder. Every document of ethnopharmacological, phytochemical or pharmacological relevance and written in English or French were analyzed.

RESULTS AND DISCUSSION

The Nauclea genus is used as ethnomedicine all along sub-Saharan Africa. Several local populations consider Nauclea species as a major source of remedies for malaria. In this regard, two improved traditional medicines are currently under development using extracts from N. latifolia and N. pobeguinii. Concerning the chemical composition of the Nauclea genus, indoloquinolizidines alkaloids could be considered as the major class of compounds as they are reported in every analyzed Nauclea species, with numerous structures identified. Based on traditional indications a considerable amount of pharmacological studies were conducted to ensure activity and attempt to link them to the presence of particular compounds in plant extracts.

CONCLUSION

Many experimental studies using plant extracts of the African species of the genus Nauclea validate traditional indications (e.g. malaria and pain). However, bioactive compounds are rarely identified and therefore, there is a clear need for further evaluations as well as for toxicity experiments. The sustainability of these plants, especially of N. diderrichii, a threatened species, should be kept in mind to adapt local uses and preparation modes of traditional remedies.

Therapeutic Potential of Spirooxindoles as Antiviral Agents

Antiviral therapeutics with profiles of high potency, low resistance, panserotype, and low toxicity remain challenging, and obtaining such agents continues to be an active area of therapeutic development. Due to their unique three-dimensional structural features, spirooxindoles have been identified as privileged chemotypes for antiviral drug development. Among them, spiro-pyrazolopyridone oxindoles have been recently reported as potent inhibitors of dengue virus NS4B, leading to the discovery of an orally bioavailable preclinical candidate (R)-44 with excellent in vivo efficacy in a dengue viremia mouse model. This review highlights recent advances in the development of biologically active spirooxindoles for their antiviral potential, primarily focusing on the structure-activity relationships (SARs) and modes of action, as well as future directions to achieve more potent analogues toward a viable antiviral therapy.