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Cinnamomum camphora (L.) J. Presl can produce an abundance of terpenoids, and has four main chemotypes: linalool, eucalyptol, camphor, and borneol. Antioxidant activity and the chemical composition of extracts from the four chemotypes were investigated during spring (May), summer (July), and autumn (November) with the aim of developing natural antioxidants using suitable chemotypes of C. camphora in suitable seasons, together with their main terpenoids. The main antioxidant terpenoids were identified. The four chemotype extracts showed strong scavenging activity against 2,2-diphenyl-1picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) free radicals as well as O 2 -• and •OH in July, due to the fact that their terpenoid content was at its highest during this month. Among the four chemotypes, the strongest scavenging activity was mainly detected in the linalool chemotype extracts, which had the highest terpenoid content. Among the ten main terpenoids in C. camphora extracts, ocimene, linalool, β-pinene, longifolene and eucalyptol showed stronger scavenging activity against DPPH free radicals, and ocimene exhibited the strongest scavenging activity. Extracts from the four chemotypes of C. camphora and their main terpenoids have the potential for development as natural antioxidants, with summer as the best season, linalool chemotypes as the optimum choice, and ocimene as the optimum compound.

Natural allelochemicals are considered as a source of algaecides. To uncover the anti-algal activity of Cinnamomum camphora fallen leaves and promote their usage as algaecides, the composition of their water and methanol extracts was analyzed, and the inhibitory effects of extracts on the growth of Microcystis aeruginosa and Chlamydomonas reinhardtii, and chlorophyll (Chl) content and photosynthetic abilities in C. reinhardtii were investigated. Twenty-five compounds were detected in the water extracts, mainly including terpenoids, esters, alcohols, and ketones. Compared to water extracts, there were more compounds and higher concentration in methanol extracts. Both water and methanol extracts inhibited the growth of the two algae, and 15 mg·ml methanol extracts killed the algal cells after 48 h. The levels of Chl a and Chl b, as well as maximum quantum yield of photosystem II photochemistry (Fv/Fm) in C. reinhardtii cells reduced gradually with increasing the concentration of extracts, while the maximum quantum yield of non-photochemical de-excitation (φD) increased gradually. At the same concentration, methanol extracts showed stronger inhibitory effects than water extracts, due to their higher number of compounds and higher concentration. Therefore, C. camphora fallen leaves have a potential value as an algaecide.

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