( ( Most ( of ( these compounds ) ) ) ( ( were ( ( polynuclear ( aromatic hydrocarbons ) ) ( -LRB- ( PAHs -RRB- ) ) ) ) . ) )
(ROOT (S (NP (NP (JJS Most)) (PP (IN of) (NP (DT these) (NNS compounds)))) (VP (VBD were) (NP (NP (JJ polynuclear) (JJ aromatic) (NNS hydrocarbons)) (PRN (-LRB- -LRB-) (NP (NNP PAHs)) (-RRB- -RRB-)))) (. .)))
Most of these compounds were polynuclear aromatic hydrocarbons (PAHs).
(ROOT (S (NP (DT A) (NN lipid)) (VP (VBZ is) (NP (NP (CD one)) (PP (IN of) (NP (NP (DT a) (ADJP (RB highly) (JJ diverse)) (NN group)) (PP (IN of) (NP (NP (NNS compounds)) (VP (VBN made) (PRT (RP up)) (ADVP (RB mostly))))) (PP (IN of) (NP (NNS hydrocarbons))))))) (. .)))