Tomato plant leaves: From by-products to the management of enzymes in chronic diseases

Lycopersicon esculentum Mill. is one of the world's most important crops and its enormous by-products, such as leaves, are an excellent source of bioactive compounds with potential application in several industries. In this work, extracts from tomato plant leaves (cultivars: Caramba, Valentine, Negro, Abuela, Rio Alto, Anairis, Rosa and Yack) were examined, for the first time, to establish their phytochemical fingerprint and capacity to inhibit key enzymes involved in Alzheimeris disease (AD) (acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) and 5-lipoxygenase (LOX)) and in diabetes mellitus (DM) (alpha-glucosidase and alpha-amylase). The hydromethanol extracts were shown to contain high amounts of phenolics (3774-9252 mu g g(-1) of dry extract), quercetin-3-0-rutinoside, quercetin-3-0-pentosyl-rutinoside, and chlorogenic and neochlorogenic acids being the major ones. The acetone extracts rich in pigments, namely chlorophylls (46.40 +/- 3.81-136.4 +/- 7.94 mg g(-1) of dry extract), as well as alkaloids extracts rich in tomatine (224 +/- 4.39-745 +/- 4.96 mg g(-1) of dry extract), were also analysed. Moreover, hydromethanol extracts exhibited inhibitory activity against AChE (IC50 = 3806 +/- 113-9911 +/- 50.5 mu g mL(-1)), BuChE (IC50 = 133.1 +/- 2.68-369.1 +/- 17.2 mu g mL(-1)), LOX (IC25 = 35.2 +/- 0.49-533 +/- 8.9 mu g mL(-1)), alpha-glucosidase (IC50 = 1.14 +/- 0.04-6.48 +/- 0.13 mg mL(-1)) and a amylase (IC50 = 1.11 +/- 0.02-1.78 +/- 0.03 mg mL(-1)). On the contrary, the alkaloid extracts were only effective against BuChE (IC50 = 82.4 +/- 1.34-172 +/- 10.2 mu g mL(-1)). Chemical fingerprint and biological activities varied according to the analysed cultivar. Overall, our results suggest that L. esculentum leaves are promising by-products and valuable sources of bioactive compounds for AD and DM management. (C) 2016 Elsevier B.V. All rights reserved.