Zostera (Les and Tippery, 2013)

Zidorn, Christian, 2016, Secondary metabolites of seagrasses (Alismatales and Potamogetonales; Alismatidae): Chemical diversity, bioactivity, and ecological function, Phytochemistry 124, pp. 5-28 : 19-20

3.15. Zostera (9, Zosteraceae, cold to warm coastal waters worldwide but excluding the tropics)

Following Borum and Greve (2004), we consider Zostera angustifolia to be part of Z. marina and Zostera nana to be a synonym of Z. noltii . Z. marina collected off the coast of Plymouth, UK, yielded five ssavonoid 7- O -sulfate derivatives 49, 59, 63–64, and 69 ( Harborne and Williams, 1976). Z. noltii (as Z. nana ) was found to also contain 59 and 64 in the same study ( Harborne and Williams, 1976). By implication, it might be assumed that the sulfated ssavonoids detected in a sample of Z. marina (as Z. angustifolia ) collected off the coast of Devon were assignable to 59, 64, and 69. Harborne’s (1975) review on ssavonoid sulfates contains neither additional data for the occurrence of these compounds in Zostera nor for other seagrass genera. Quackenbush et al. (1986) described an early RP-HPLC method for phenolic acids in Z. marina . Based on retention times, the authors detected 10, 13, 14, 16, 18, 28, and 29 in an extract of Z. marina collected off the coast of the US state of Washington. Apart from general concerns on the suitability of HPLC retention times as the sole criterion for compound identification, the presented data (HPLC retention times and their standard deviations for pure compounds and the allegedly same compounds in a Z. marina extract), indicate that the presence of the above mentioned should be confirmed in Z. marina using more appropriate techniques. Also using HPLC retention times, Vergeer and Develi (1997) identified 16, 25, 28, and 29 in Z. marina leaves collected off the coast of Brittany, France. In this study on top of the concerns raised above, the extraction procedure was so harsh that artefact formation seems to be likely. So even if the compounds were indeed present in the analyzed extracts, it remains unclear whether they were genuine natural products or artefacts (or at least partially so, i.e. the natural products could still occur as genuine natural products but not in the amounts implied by the quantification results). Buchsbaum et al. (1990) confirmed the presence of 59 and 63 in Z. marina .

Zosteric acid 26 was first discovered by Todd et al. (1993) in Z. marina . Due to its interesting antifouling bioactivities (see Sections 4.2 and 4.5 below), even detritus derived from Zostera leaves was investigated as a potential source of 26 ( Achamlale et al., 2009). In this study, also Z. noltii was detected to contain 26. Z. marina collected off the coast of Qingdao, China, yielded rosmarinic acid 32 (Wang et al., 2012). In an interesting study unfortunately limited to only four sampling sites, Grignon-Dubois et al. (2012) investigated regional differences in the contents of 26, 28, and 32 in Z. noltii . The authors observed huge absolute differences in amounts (potentially related to a different status of defence against potential pathogens but potentially also due to genetic differences) of the quantified phenolic acids while the relative amounts of these compounds varied only marginally (with rosmarinic acid 32 being the most and caffeic acid 28 the least abundant compound).