While consumption of the root of the sweet potato plant is very common, and is known to be a a good source of vitamin C and certain B vitamins that are considered essential to human health, the consumption of other parts of the plant is less common – despite the fact that they are edible and high in nutritional value.
Writing in HortScience, researchers analysed the levels of a variety of vitamins and essential nutrients in different tissues of the sweet potato plant – finding that both mature and young leaves can provide significant amounts of vitamin B6 and other essential vitamins.
"These results confirm previous studies that sweet potato foliar tissues are a good source of ascorbic acid, and that young leaves have the highest foliar ascorbic acid content," the US-based researchers noted.
The team, led by Wilmer Barrera and David Picha from Louisiana State University Agricultural Center, concluded that ascorbic acid, riboflavin, and vitamin B6 contents were higher in leaf tissue than in other tissue types.
"Our results indicate that mature and young leaves of sweet potato could provide significant amounts of vitamin B6 to the human diet," they said – adding that the vitamin B6 content in sweet potato leaves compares well with fruits and vegetables including broccoli, avocados, carrots, bananas, and cauliflower.
"The objective of the study was to determine the ascorbic acid, thiamin, riboflavin, and vitamin B6 content in a wide range of edible tissues of 'Beauregard' and 'LA 07-146' sweet potatoes, two important commercial cultivars in Louisiana," explained Barrera and Picha.
The team analysed a variety of sweet potato tissue types (mature leaves, young leaves, young petioles, buds, vine sections, and root tissue) from a sweet potato plot at Louisiana State University on two occasions before conducting a third experiment to study water-soluble vitamin content among different sweet potato root tissues.
Their analyses revealed differences in total ascorbic acid (AA) content among tissue types – showing that young leaves contained the highest AA content, followed by mature leaves and buds.
Buds also contained significantly higher AA content than sweet potato roots, vines, and petiole tissues, they said.
Results also showed that riboflavin content differed with sweet potato tissue type, but was consistently higher in the leaves; mature leaves contained higher amounts of riboflavin than young leaves and other plant tissues, including roots.
"Leaf tissue also contained higher total vitamin B6 content compared with other tissues,” revealed the authors. “Mature leaves contained 3.4 times higher vitamin B6 than roots, whereas mature petioles contained 2.3 times more than roots.
Bud tissue and young leaves also contained higher B6 levels than roots, they added.