Seasonal variation of total phenolic content in six lettuce cultivars grown with microbiological fertilizer

Abstract

Lettuce (Lactuca sativa, L.) is an annual, cool season crop belonging to Asteraceae family and to a group of leafy vegetables. It is rich in minerals, vitamins and antioxidative compounds which are essential for human nutrition. The advantage of lettuce, as eaten raw, is that maintains more nutrients than other cooked vegetables. Lettuce is low in calories and it is suggested to diabetics, people with sleep problems and disturbed metabolism. Growers are interested in cultivating lettuce because of their short vegetation period and opportunity to cultivate in all seasons. The purpose of this study was to examine the effect of microbiological fertilizer Em Aktiv (Candor) on the total phenolic content (TPC) in six lettuce cultivars. Cultivars (′Kiribati′, ′Murai′, ′Aquino′, ′Gaugin′, ′Aleppo′, ′Carmesi′- Rijk Zwaan) were grown in the fertile soil in a greenhouse experiment during three successive seasons (autumn, winter and spring). Total phenolic content ranged between 175.85-372.73 μg GAE/g FW in autumn, 104.12-522.74 μg GAE/g FW in winter and 88.88-340.93 μg GAE/g FW in spring. Our results indicated that red cultivars mainly had higher total phenolic content compared to green cultivars with the exception in autumn experiment. Among all seasons, control treatment of cultivar ′Carmesi′ showed the highest total phenolic content (522.74 μg GAE/g FW) in winter. The effect of fertilizer Em Aktiv on TPC in different cultivars was to some extent positive in spring and autumn, but even negative during winter season. Such a complex response indicates the need for careful selection of varieties and fertilizers in relation to the season. To conclude, red cultivars were pointed out with higher total phenolic content and they could be recommended as a great source of bioactive compounds for healthy human diet.

Salata (Lactuca sativa, L.) je jednogodišnja vrsta, prohladne klime koja pripada familiji Asteraceae i grupi lisnatog povrća. Bogata je mineralima, vitaminima, antioksidantima koji su neophodni u ljudskoj ishrani. Prednost salate, kao sirovog povrća, je da sadrži više hranljivih materija u odnosu na drugo termički obrađeno povrće. Salata ima nisku kalorijsku vrednost i preporučuje se u ishrani dijabetičara, ljudi sa poremećenim ritmom spavanja i metabolizma. Proizvođači su zainteresovani za gajenje salate zbog kratkog vegetacionog perioda i mogućnosti gajenja tokom cele godine. Cilj ovog istraživanja bio je da se utvrdi uticaj mikrobiološkog đubriva Em Aktiv (Candor) na sadržaj ukupnih fenola (TPC) kod šest sorti salate. Sorte (′Kiribati′, ′Murai′, ′Aquino′, ′Gaugin′, ′Aleppo′, ′Carmesi′- Rijk Zwaan) su gajene na plodnom zemljištu u plasteniku tokom tri uzastopne sezone (jesen, zima i proleće). Sadržaj ukupnih fenola kretao se u jesen između 175.85-372.73 μg GAE/g FW, u zimu 104.12-522.74 μg GAE/g FW i u proleće 88.88-340.93 μg GAE/g FW. Rezultati ukazuju da su crvene sorte uglavnom pokazale veći sadržaj ukupnih fenola u odnosu na zelene sorte sa izuzetkom jesenjeg ogleda. Među svim sezonama, najveći sadržaj ukupnih fenola određen je u kontroli kod sorte ′Carmesi′ (522.74 μg GAE/g FW) u zimskom ogledu. Uticaj đubriva Em Aktiv na sadržaj ukupnih fenola, kod različitih sorti salate, u određenom opsegu bio je pozitivan u proleće i jesen pa čak i negativan tokom zime. Ovako složen odgovor ukazuje na potrebu za pažljivim odabirom varijeteta salate i đubriva u odnosu na sezonu. Na osnovu dobijenih rezultata može se zaključiti da su crvene sorte salate pokazale veći sadržaj ukupnih fenola i mogu se preporučiti kao izvor bioaktivnih supstanci u zdravoj ishrani.