There are several factors that may induce ulcers in human beings such as stress, chronic use of anti-inflammatory drugs, etc. Though in most cases, the etiology of ulcer is unknown, it has generally accepted that it is the result of an imbalance between aggressive factors and maintenance of the mucosal integrity through the endogenous defense mechanism. For centuries, many kinds of native plants and their products have been used for the treatment of peptic ulcers by traditional healers in Phayaoprovince. The current study aimed to investigate the polyphenol content in some of these medicinal plants and to point out the antiulcer activity. In this study, we assessed for antiulcer activities with aqueous extract and in-vitro method as the acid neutralizing capacity and H+/K+ - ATPase inhibition activity method and in acid-neutralizing capacity (ANC), the extract significantly reduced ANC to 9.33 at a concentration of 1500 mg as compared to 15.7 with standard Aluminium hydroxide + Magnesium hydroxide (500mg).