The alkaloid extract of the aerial parts of Psychotria myriantha (Rubiaceae) displayed antichemotactic activity on polymorphonuclear leukocytes (PMN) assessed by the Boyden chamber assay. On analysis of the crude extract by LC/APCI/MS and LC/UV/DAD, two major constituents could be detected. In order to rapidly identify the active compounds, a microfractionation was conducted during LC/UV/DAD analysis. By this means, both the collected compounds could be assayed separately in the Boyden chamber and were shown to inhibit PMN chemotaxis. Their isolation was performed by semi-preparative HPLC and their structures elucidated by classical spectroscopic methods, including UV, NMR, MS and HRMS. Both compounds showed characteristics of monoterpene indole glucoside alkaloids; one of them was identified as strictosidinic acid and the other was a new natural product, myrianthosine. The antichemotactic activity of the compounds may be related to an antiacute inflammation activity.