About 5,000 strains of actinomyctes were isolated from near coast. It was found that 2,600 strains have independent sequence. Additionally, 386 strains showed less than 98% homology with BLAST Search. Througn the search of rare actinomycete strains, less than 98% homology, six novel tricyclic acids of a new structure class, indoxamycins A-F 1-6), and two aromatic acids, lorneic acid A-B (7-8), were isolated from a saline culture medium of these strains. The chemical structures of these compounds were assigned by combine spectral and chemical methods. Indoxamycins A-F (1-6) were isolated from the culture medium of NPS643 (96% sequence homology). Growth inhibition activities (HT-29) of indoxamycins were identified as indoxamycin A (1) (IC_<50> 0.59μM), indoxamycin F (6) (IC_<50> 0.33μM). On the other hand, hydroxyl methyl analogs of 1, indoxamycin B-E (2-5), showed no activity at 3μM. Feeding experiment of ^<13>C-propionic acid revealed that tricyclic ring system was build from 6 propionate units. Lorneic acid A-B (7-8) were isolated from the culture medium of NPS554 (98% sequence homology). These acids showed very week growth inhibition activities against TF-1 cell (7: 98%, 8: 81%, 500μM). However, according to the enzyme inhibition activities against 150 targets, lorneic acid A (7) showed specific inhibition against pepsin (inhibition ratio: 88%, 10μM) and phosphodiesterase 5 (inhibition ratio: 50%, 10μM). Evaluation of their biological activities and detailed analysis of biosynthetic mechanisms are currently under infestigation.
