The lack of vaccines and antiviral treatment, along with the increasing number of cases of Zika virus (ZIKV) and Chikungunya virus (CHIKV) infections, emphasize the need for searching for new therapeutic strategies. In this context, the marine brown seaweed Canistrocarpus cervicornis has been proved to hold great antiviral potential. Hence, the aim of this work was to evaluate the anti-ZIKV and anti-CHIKV activity of a marine dolastane isolated from brown seaweed C. cervicornis and its crude extract. Vero cells were used in antiviral assays, submitted to ZIKV and CHIKV, and treated with different concentrations of C. cervicornis extract or dolastane. The crude extract of C. cervicornis showed inhibitory activities for both ZIKV and CHIKV, with EC₅₀ values of 3.3 μg/mL and 3.1 μg/mL, respectively. However, the isolated dolastane showed a more significant and promising inhibitory effect (EC₅₀ = 0.95 µM for ZIKV and 1.3 µM for CHIKV) when compared to both the crude extract and ribavirin, which was used as control. Also, the dolastane showed a very potent virucidal activity against CHIKV and was able to inhibit around 90% of the virus infectivity at 10 μM. For the ZIKV, the effects were somewhat lower, although interesting, at approximately 64% in this same concentration. Further, we observed that both the extract and the dolastane were able to inhibit the replication of ZIKV and CHIKV at different times of addition post-infection, remaining efficient even if added after 8 hours post-infection, but declining soon after. A synergistic effect using sub-doses of the extract and isolates was associated with ribavirin, inhibiting above 80% replication even at the lowest concentrations. Therefore, this work has unveiled the anti-ZIKV and CHIKV potential of C. cervicornis crude extract and an isolated dolastane, which, in turn, can be used as a preventive or therapeutic strategy in the future.

Oral squamous cell carcinoma (OSCC) is a global public health problem with high incidence and mortality. The chemotherapeutic agents used in the clinic, alone or in combination, usually lead to important side effects. Thus, the discovery and development of new antineoplastic drugs are essential to improve disease prognosis and reduce toxicity. In the present study, acridine-core naphthoquinone compounds were synthesized and evaluated for their antitumor activity in OSCC cells. The mechanism of action, pharmacokinetics, and toxicity parameters of the most promising compound was further analyzed using in silico, in vitro, and in vivo methods. Among the derivatives, compound 4e was highly cytotoxic (29.99 µM) and selective (SI 2.9) at levels comparable and generally superior to chemotherapeutic controls. Besides, compound 4e proved to be non-hemolytic, stable, and well tolerated in animals at all doses tested. Mechanistically, compound 4e promoted cell death by apoptosis in the OSCC cell, and molecular docking studies suggested this compound possibly targets enzymes important for tumor progression, such as RSK2, PKM2, and topoisomerase IIα. Importantly, compound 4e presented a pharmacological profile within desirable parameters for drug development, showing promise for future preclinical trials.

Oral squamous cell carcinoma (OSCC) is a worldwide public health problem, accounting for approximately 90% of all oral cancers, and is the eighth most common cancer in men. Cisplatin and carboplatin are the main chemotherapy drugs used in the clinic. However, in addition to their serious side effects, such as damage to the nervous system and kidneys, there is also drug resistance. Thus, the development of new drugs becomes of great importance. Naphthoquinones have been described with antitumor activity. Some of them are found in nature, but semi synthesis has been used as strategy to find new chemical entities for the treatment of cancer. In the present study, we promote a multiple component reaction (MCR) among lawsone, arylaldehydes, and benzylamine to produce sixteen chemoselectively derivated Mannich adducts of 1,4-naphthoquinones in good yield (up to 97%). The antitumor activities and molecular mechanisms of action of these compounds were investigated in OSCC models and the compound 6a induced cytotoxicity in three different tumor cell lines (OSCC4, OSCC9, and OSCC25) and was more selective (IS > 2) for tumor cells than the chemotropic drug carboplatin and the controls lapachol and shikonin, which are chemically similar compounds with cytotoxic effects. The 6a selectively and significantly reduced the amount of cell colony growth, was not hemolytic, and tolerable in mice with no serious side effects at a concentration of 100 mg/kg with a LD₅₀ of 150 mg/kg. The new compound is biologically stable with a profile similar to carboplatin. Morphologically, 6a does not induce cell retraction or membrane blebs, but it does induce intense vesicle formation and late emergence of membrane bubbles. Exploring the mechanism of cell death induction, compound 6a does not induce ROS formation, and cell viability was not affected by inhibitors of apoptosis (ZVAD) and necroptosis (necrostatin 1). Autophagy followed by a late apoptosis process appears to be the death-inducing pathway of 6a, as observed by increased viability by the autophagy inhibitor (3-MA) and by the appearance of autophagosomes, later triggering a process of late apoptosis with the presence of caspase 3/7 and DNA fragmentation. Molecular modeling suggests the ability of the compound to bind to topoisomerase I and II and with greater affinity to hPKM2 enzyme than controls, which could explain the mechanism of cell death by autophagy. Finally, the in-silico prediction of drug-relevant properties showed that compound 6a has a good pharmacokinetic profile when compared to carboplatin and doxorubicin. Among the sixteen naphthoquinones tested, compound 6a was the most effective and is highly selective and well tolerated in animals. The induction of cell death in OSCC through autophagy followed by late apoptosis possibly via inhibition of the PKM2 enzyme points to a promising potential of 6a as a new preclinical anticancer candidate.