Investigation of phytochemicals and bioactive properties of rootless duckweed (Wolffia arrhiza) extracted by supercritical carbondioxide extraction

Wolffia (rootless duckweed), a free-floating aquatic plant from the Lemnaceae family, is the world's smallest flowering plant. Wolffia, consumed as food in some parts of Southeast Asia, are called "water eggs" due to their high protein content. This species is not yet recognized in Turkey. In this study, Wolffia arrhiza collected from wetlands in Yeşilırmak Delta (Samsun) was grown under different LED lights (white, red, blue, purple) under controlled laboratory conditions. The relative growth rate, dry matter and ash analysis, elemental content and photosynthetic pigments (chlorophyll and carotenoid content) of the plant were analyzed. In vitro antioxidant and antimicrobial activities of extracts obtained by supercritical carbon dioxide extraction were examined, and their phytochemical content was analyzed by gas chromatography-mass spectrometry (GC-MS). In different wavelength applications, red LED light increased the photosynthetic pigment content, phenolic substance and flavonoid amount and antioxidant activity of W. arrhiza. White LED light increased the amount of dry matter (20.69%) and growth rate (0.732 day-1). The highest protein content (55.3%) was detected in W. arrhiza grown under purple LED light. In the antimicrobial activity analysis, moderate levels were observed on Bacillus cereus. As a result of GC-MS analysis performed on the hexane solution of extracts obtained by SC-CO2 extraction of W. arrhiza, 43 different bioactive phytoconstituents were identified. 22, 37, 35 and 43 phytocomponents were tested in W. arrhiza grown under different LED lights, respectively, in white, red, purple and blue LEDs. It has been determined that W. arrhiza contains very valuable phytosterols such as campesterol, stigmasterol, β-sitosterol, which should be present in the diet in abundance. 44% phytosterol was recorded in white LED light, 37% in red LED light, 39% in violet LED light, and 22% in blue LED light. This study is the first to evaluate the extract of rootless duckweed W. arrhiza obtained by the SCE method. The study showed that different LED lighting can increase the plant's ability to synthesize a wide variety of bioactive substances in the desired amount. In addition, it has been clearly demonstrated that providing access to more and more diverse secondary metabolites without using solvents with the SK-CO2 extraction method used will lead to promising developments in the fields of alternative food production and pharmaceutical active ingredient production. Since rootless duckweed is easy to produce, environmentally friendly and sustainable, its use as a functional food is seen as an important potential. In addition to the nutraceutical properties of rootless duckweed, which is a superfood, its pharmaceutical properties are also promising and need to be evaluated.