Chemical components with antitumour activity from Inula britannica

The flowers of Inula britannica L. are widely used for their significant antitumour and anti-inflammatory properties. However, the other parts of the plant, including the stems, leaves and roots, remain underutilised. Herein, 18 compounds, including 5 previously undescribed compounds (1-5), were isolated from these underutilised parts, and their structures were elucidated by HRESIMS, NMR and ECD spectroscopic analyses. Several isolated sesquiterpenes (7-9) exhibited significant inhibitory activity against three tumour cell lines. In addition, eight compounds (2-4, 11, 13 and 16-18) showed synergistic effects in combination with cisplatin in SKOV3 cells. Notably, compound 8 significantly inhibited SKOV3 xenograft tumour growth without apparent toxicity. These findings demonstrate that the underutilised parts of I. britannica contain novel sesquiterpenes with promising antitumour activity, warranting further investigation.