Sea hares (family Aplysiidae) are a rich source of bioactive substances. Especially, over the past 40 years, the genera Aplysia and Dolabella have afforded numerous bioactive secondary metabolites that exhibit antitumor activity. For example, the depsipeptide dolastatin 10 and its analogue are currently in cancer clinical trials. Meanwhile, the chemical probe approach has revealed that the antitumor macrolide aplyronine A inhibits microtubule assembly in association with actin. This article highlights the recent findings regarding the chemical biology of antitumor and antineoplastic compounds from sea hares, as well as molecules that have been discovered and characterized after 2000.Keywords Antitumor · Sea hare · Aplysia · Antitumor · Actin-deplymerization · Cytotoxicity · Tubulin
IntroductionSea hares, which belong to the opisthobranch group of mollusks (clade Aplysiomorpha), are shell-less, slow-moving benthic marine mollusks [1]. The order Anaspidea includes two families, Akeridae and Aplysiidae [2]. Almost all chemical studies have focused on Aplysiidae specimens. The family Aplysiidae includes nine genera, Aplysia (Linnaeus 1767), Bursatella (Blainville 1817), Dolabella (Lamarck 1801), Dolabrifera (Gray 1847), Notarchus (Cuvier 1817), Petalifera (Gray 1847), Phyllaplysia (Fischer 1872), Syphonota (Adams 1854), and Stylocheilus (Gould 1852). Sea hares are herbivorous, and are typically found on seaweed in shallow water. They are not eaten by other marine animals and have been postulated to contain chemical defense substances. The poisonous properties of sea hare secretions were known in Roman times. In addition, sea hares release ink from their ink glands, which deter predators. This ink acts as a screen, while at the