The present invention discloses (1) phenolic ester hybrids of niacin with m-methoxy-p-hydroxy phenyl compounds like eugenol, vanillin, apocynin, ferulic acid, isoferulic acid and eugenol epoxide and (2) cocrystals of hybrids as above, particularly cocrystal of niacin-eugenol hybrid with cocrystal former like eugenol and oxalic acid (3) novel pharmaceutical compositions comprising a combination of niacin and one or more small molecule/potentiating agent like eugenol, curcumin, cinnamic acid, meclofenamic acid, and their use in the treatment of a disorder or a disease caused by excess production of amyloid beta peptide-42 (Aβ42), its deposition, accumulation, and plaque formation including Alzheimers Disease, dementia and mild cognitive impairment as well as other neurodegenerative diseases such as Parkinsons Disease and ischemic stroke.