Isobutyrylshikonin has a potentially stronger cytotoxic effect in oral cancer cells than its analogue shikonin in vitro

A Review on Shikonin and Its Derivatives as Potent Anticancer Agents Targeted against Topoisomerases

The topoisomerases (TOPO) play indispensable roles in DNA metabolism, by regulating the topological state of DNA. Topoisomerase I and II are the well-established drug-targets for the development of anticancer agents and antibiotics. These drugs-targeting enzymes have been used to establish the relationship between drug-stimulated DNA cleavable complex formation and cytotoxicity. Some anticancer drugs (such as camptothecin, anthracyclines, mitoxantrone) are also widely used as Topo I and Topo II inhibitors, but the poor water solubility, myeloma suppression, dose-dependent cardiotoxicity, and multidrug resistance (MDR) limited their prolong use as therapeutics. Also, most of these agents displayed selective inhibition only against Topo I or II. In recent years, researchers focus on the design and synthesis of the dual Topo I and II inhibitors, or the discovery of the dual Topo I and II inhibitors from natural products. Shikonin (a natural compound with anthraquinone skeleton, isolated from the roots of Lithospermum erythrorhizon) has drawn much attention due to its wide spectrum of anticancer activities, especially due to its dual Topo inhibitive performance, and without the adverse side effects, and different kinds of shikonin derivatives have been synthesized as TOPO inhibitors for the development of anticancer agents. In this review, the progress of the shikonin and its derivatives together with their anticancer activities, anticancer mechanism, and their structure-activity relationship (SAR) was comprehensively summarized by searching the CNKI, PubMed, Web of Science, Scopus, and Google Scholar databases.

Review of Shikonin and Derivatives: Isolation, Chemistry, Biosynthesis, Pharmacology and Toxicology

Shikonin and its derivatives, isolated from traditional medicinal plant species of the genus Lithospermum, Alkanna, Arnebia, Anchusa, Onosma, and Echium belonging to the Boraginaceae family, have numerous applications in foods, cosmetics, and textiles. Shikonin, a potent bioactive red pigment, has been used in traditional medicinal systems to cure various ailments and is well known for its diverse pharmacological potential such as anticancer, antithrombotic, neuroprotective, antidiabetic, antiviral, anti-inflammatory, anti-gonadotropic, antioxidants, antimicrobial and insecticidal. Herein, updated research on the natural sources, pharmacology, toxicity studies, and various patents filed worldwide related to shikonin and approaches to shikonin’s biogenic and chemical synthesis are reviewed. Furthermore, recent studies to establish reliable production systems to meet market demand, functional identification, and future clinical development of shikonin and its derivatives against various diseases are presented.

Shikonin, a naphthalene ingredient: Therapeutic actions, pharmacokinetics, toxicology, clinical trials and pharmaceutical researches

BACKGROUND

Shikonin is one of the major phytochemical components of Lithospermum erythrorhizon (Purple Cromwell), which is a type of medicinal herb broadly utilized in traditional Chinese medicine. It is well established that shikonin possesses remarkable therapeutic actions on various diseases, with the underlying mechanisms, pharmacokinetics and toxicological effects elusive. Also, the clinical trial and pharmaceutical study of shikonin remain to be comprehensively delineated.

PURPOSE

The present review aimed to systematically summarize the updated knowledge regarding the therapeutic actions, pharmacokinetics, toxicological effects, clinical trial and pharmaceutical study of shikonin.

METHODS

The information contained in this review article were retrieved from some authoritative databases including Web of Science, PubMed, Google scholar, Chinese National Knowledge Infrastructure (CNKI), Wanfang Database and so on, till August 2021.

RESULTS

Shikonin exerts multiple therapeutic efficacies, such as anti-inflammation, anti-cancer, cardiovascular protection, anti-microbiomes, analgesia, anti-obesity, brain protection, and so on, mainly by regulating the NF-κB, PI3K/Akt/MAPKs, Akt/mTOR, TGF-β, GSK3β, TLR4/Akt signaling pathways, NLRP3 inflammasome, reactive oxygen stress, Bax/Bcl-2, etc. In terms of pharmacokinetics, shikonin has an unfavorable oral bioavailability, 64.6% of the binding rate of plasma protein, and enhances some metabolic enzymes, particularly including cytochrome P450. In regard to the toxicological effects, shikonin may potentially cause nephrotoxicity and skin allergy. The above pharmacodynamics and pharmacokinetics of shikonin have been validated by few clinical trials. In addition, pharmaceutical innovation of shikonin with novel drug delivery system such as nanoparticles, liposomes, microemulsions, nanogel, cyclodextrin complexes, micelles and polymers are beneficial to the development of shikonin-based drugs.

CONCLUSIONS

Shikonin is a promising phytochemical for drug candidates. Extensive and intensive explorations on shikonin are warranted to expedite the utilization of shikonin-based drugs in the clinical setting.