( ( ( The ( main action ) ) ( of gastrin ) ) ( ( is ( stimulation ( of ( gastric ( acid ( and ( pepsin secretion ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ main) (NN action)) (PP (IN of) (NP (NN gastrin)))) (VP (VBZ is) (NP (NP (NN stimulation)) (PP (IN of) (NP (JJ gastric) (NN acid) (CC and) (NN pepsin) (NN secretion))))) (. .)))
The main action of gastrin is stimulation of gastric acid and pepsin secretion.
(ROOT (S (NP (NNP Gastrin)) (VP (VBZ signals) (NP (NP (DT the) (NN secretion)) (PP (IN of) (NP (JJ gastric) (NN acid))))) (. .)))