<jats:title>Abstract</jats:title><jats:p>Alkaloids <jats:bold>1</jats:bold>‐<jats:bold>4</jats:bold> from <jats:italic>Cynanchum vincetoxicum</jats:italic> (asclepiadaceae) (Scheme 1) do not have affinity to the oestrogen receptor but they inhibit the growth of the hormone‐independent mammary carcinoma cells MDA‐MB‐231 (Fig. 1) and bind to nucleosides and nucleotides (Table 1). Intercalation was not observed.