Seaweeds are used in traditional agriculture practices because of their beneficial effects. Recently, the rising demand for organically grown foods has amplified the use of organic fertilizers such as seaweed extracts. Despite their beneficial effects, few studies have reported information about compounds in seaweed extracts that are responsible for these benefits. Thus, the aim of this study was to evaluate the potential relationships between the components and secondary metabolites in four seaweed liquid extracts from Eisenia arborea, Macrocystis pyrifera, Padina caulescens, and Sargassum horridum and their biostimulant activity through changes in the germination, growth, and protein content of tomato seedlings (Solanum lycopersicum). The E. arborea and S. horridum extracts showed similar compositions (ash, organic carbon, bicarbonates, and chlorides), minerals (Ca, Fe, and Cu) and secondary metabolites (triterpenes and saponins), albeit with different component concentrations. The chemical composition of the P. caulescens extract was significantly different from those of the other extracts; it was characterized by high levels of total nitrogen, phenols, and carbohydrates. Almost all seaweed extracts had beneficial effects on seed germination and seedling length, except the S. horridum extract that inhibits germination. The hierarchical clustering plots and principal component analysis indicated that germination and protein content are related to the presence of sterol. Shoot length was closely related to mineral levels (K, Zn, B, Na) and the C:N ratio, whereas radicle length was closely related to the content of nitrogen, carbohydrates, phenols, and flavonoids in the seaweed extracts. However, the underlying mechanisms are still unclear and require further studies.

Cucurbita foetidissima and C. radicans are scarcely studied wild pumpkin species that grow in arid and semi-arid areas of Mexico and the United States. This study describes the morphological, proximal composition, metabolic finger-prints and seed protein profiles of C. foetidissima and C. radicans fruits collected in the wild during a one-year period in different locations of central-western Mexico. The results obtained complement the limited information concerning the fruit composition of C. foetidissima and greatly expand information in this respect regarding C. radicans. Morphology and proximal composition of their fruits varied significantly. Different metabolic fingerprints and seed protein profiles were detected between them and also with the chemical composition of domesticated Cucurbita fruits. The neutral lipids in seed, pulp and peels were rich in wax content and in unsaturated compounds, probably carotenoids and tocopherols, in addition to tri-, di- and mono-acylglycerols. The tri- and diacylglycerol profiles of their seed oils were different from commercial seed oils and between each other. They also showed unusual fatty acid compositions. Evidence of a possible alkaloid in the pulp and peel of both species was obtained in addition to several putative cucurbitacins. An abundance of phenolic acids was found in all fruit parts, whereas flavonoids were only detected in the peels. Unlike most cucurbits, globulins were not the main protein fraction in the seeds of C. radicans, whereas the non-structural carbohydrate and raffinose oligosaccharide content in their fruit parts was lower than in other wild cucurbit species. These results emphasize the significantly different chemical composition of these two marginally studied Cucurbita species, which was more discrepant in C. radicans, despite the notion regarding C. foetidissima as an aberrant species with no affinity to any other Cucurbita species.