Nutritional value and chemical composition of purslane leaves in relation to harvest stage
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resumo
Purslane (Portulaca oleraceae L.) is an omnipresent weed, while it is also considered a common ingredient
of the Mediterranean diet due to its high nutritional value with particular reference to omega-3 fatty acids
content ln the present study, we evaluated the nutritional value and chemical composition of purslane
leaves in relation to harvesting stage. Plants were harvested at three growth stages (29, 43 and 52 days
a:fter sowing (DAS)), while leaves were separated from the aerial parts ofthe plant. Leaves contained high
amounts of macronutrients, especially at 52 DAS. a-Tocopherol was the main isoform, which increased at
52 DAS, as well as the total tocopherols (values were in the ranges of 197-327 !J.g/l 00 g fresh weight (fw)
and 302-481 !J.g/100 g fw, for a-tocopherol and total tocopherols, respectively). Glucose and fructose
were the main detected free sugars, while total sugars content ranged between O. 160 g and 0.330 g/100 g
fw). Oxalic and total organic acids content increased at late harvesting (52 DAS; 8.6 g and 30.3 g/ 100 g
fw for oxalic acid and total organic acids, respectively). Regarding the fatty acids content, leaves were
abundant in a-linolenic acid (35.4--54.92%), although a decreasing trend was observed with successive
harvesting. Oleracein A and C were the major oleracein derivatives detected in leaves, regardless ofthe
harvesting stage (values were in the ranges of8.2-103.0 mg and 21.2-143 mg/100 g dried weight (dw) for
oleraceins A and C, respectively), while the highest content was recorded at 29 DAS for both compounds.
Hepatotoxicity assays showed no toxicity with Gl50 values being higher than 400 !J.g/rnL for all the
harvesting stages. ln conclusion, early harvesting could increase the nutritional value of the final product
through increasing the content ofvaluable compounds, such as omega-3 fatty acids, phenolic compounds
and oleracein derivatives, while at the sarne time, the contents of anti-nutritional compounds such as
oxalic acid are reduced.
