Enhanced carbazole alkaloid and antioxidant capacity in callus culture of medicinal plant Clausena harmandiana by Bacilius subtilis elicitor

Clausena harmandiana (Pierre) Guillaumin (Rutaceae), is a medicinal plant native to Thailand. Its major active compounds are carbazole alkaloids, which possessed various pharmacological activities and antioxidant activity [1],[2]. Two carbazole alkaloids, clausine K and 7-methoxymukonal, are the major compounds in the callus culture of C. harmandiana [3]. Enhancing the productivity of callus culture can provide an alternative for carbazole alkaloids production and minimize destructive harvest of wild-plant materials.

To improve the productivity, we tested the effects of two biotic elicitors, Bacillus subtilis and Trichoderma harzianum, on accumulation of two carbazole alkaloids in C. harmandiana callus culture. Antioxidant activity of the callus extracts were also assessed by DPPH and FRAP assays along with total phenolic contents.

Callus was induced from C. harmandiana leaf explants cultured on Murashige and Skoog medium supplemented with 0.1 mg/L thidiazuron, 1 mg/L naphthaleneacetic acid, and 5% sucrose. A living B. subtilis culture at 0.1 and 1% (V/V) significantly enhanced clausine K level in callus up to 5-fold. However, T. harzianum did not affect carbazole alkaloids accumulation. In addition, 1% (V/V) B. subtilis and 1% (V/V) T. harzianum significantly promoted total phenolic contents in callus up to 2.5-fold. DPPH and FRAP assays indicated significant enhancement of antioxidant activities in callus treated with various concentration of B. subtilis and T. harzianum, which highly correlated to phenolic contents.

The established C. harmandiana callus culture and the used of B. subtilis as elicitor is an efficient alternative and sustainable source for production of clausine K with improved antioxidant activities.

• References

• 1 Huang L, Feng Z-L, Wang Y-T, Lin L-G. Anticancer carbazole alkaloids and coumarins from Clausena plants: A review. Chin J Nat Med 2017; 15: 881-888
• 2 Songsiang U, Thongthoom T, Zeekpudsa P, Kukongviriyapan V, Boonyarat C, Wangboonskul J, Yenjai C. Antioxidant activity and cytotoxicity against cholangiocarcinoma of carbazoles and coumarins from Clausena harmandiana . Science-Asia 2012; ; 38: 75-81
• 3 Kitisripanya T, Laoburee M, Puengsiricharoen L, Pratoomtong P, Daodee S, Wangboonskul J, Putalun W. Production of carbazole alkaloids through callus and suspension cultures in Clausena harmandiana . Nat Prod Res advance online publication 26 Dec 2018; DOI: 10.1080/14786419.2018.1533833.