The objective of the thesis is to study to clarify the main chemical composition of two species and P. gracilis in the Northeast sea of Vietnam. Evaluate the cytotoxic activity of some isolated compounds to search for bioactive compounds. | Summary of Chemistry Doctoral thesis: Study on chemical constituents and biological activities from Culcita Novaeguineae Müller & Troschel, 1842 and Pentaceraster Gracilis (Lutken, 1871) in Viet Nam