This paper presents a study about the impact of contexts in automatic semantic annotation over cross-lingual biomedical resources. Semantic annotation consists in associating parts of document texts to concepts described in some knowledge resource (KR). In this paper, we propose an unsupervised method for semantic annotation that regards contexts for validating the annotations. We test the method with two cross-lingual corpora, which allows us extracting correct annotations in the languages in the aligned corpora. Results show that annotated cross-lingual corpora provides grounds for qualitative comparison of semantic annotation algorithms.