Mitochondria-Targeting 1,5-Diazacyclooctane-Spacered Triterpene Rhodamine Conjugates Exhibit Cytotoxicity at Sub-Nanomolar Concentration against Breast Cancer Cells

Abstract

1,5-Diazacyclooctane was prepared by a simple synthetic sequence and coupled to pentacyclic triterpenoic acids oleanolic acid, ursolic acid, betulinic acid, platanic acid, and asiatic acid; these amides were activated with oxalyl chloride and reacted with rhodamine B or rhodamine 101 to yield conjugates. The conjugates were screened in SRB assays with various human breast cancer cell lines (MDA-MB-231, HS578T, MCF-7, and T47D) and found to exert cytotoxic activity even at a low concentration. Therefore, for an asiatic acid rhodamine 101 conjugate (28), an IC50 = 0.60 nM was determined and found to induce apoptosis in MDA-MB-231 and HS578T cells. Extra experiments showed the compound to act as a mitocan and to induce inhibition of proliferation or growth arrest in MDA-MB-231 cells at lower doses followed by an induction of apoptosis at higher doses. Furthermore, differential responses to proliferation inhibition and apoptosis induction may explain differential sensitivity of mammary cell lines to compound 28.

F16 Hybrids Derived from Steviol or Isosteviol Are Accumulated in the Mitochondria of Tumor Cells and Overcome Drug Resistance

“…= 194-195 • C (lit. : [35] 3089w, 3039w, 2970w, 2921w, 2881w, 1630m, 1568m, 1524w, 1499m, 1452m, 1416m, 1348br, 1281m, 1250m, 1224w, 1186w, 1153w, 1136w, 1118m, 1083w, 1042w, 1026w, 976w, 953s, 911w, 882w, 851w, 816w, 772br, 740s, 699s, 629m, 617m, 563w, 548w, 7.56 (d,J = 16.6 Hz,1H,7.45 (d,J = 7.8 Hz,1H,7.34 (dd,J = 7.9,4.7 Hz,1H,7.14 (td,J = 7.4,6.8,1.2 Hz,1H,7.12 (d,J = 16.6 Hz,1H, ppm; 13 C NMR (126 MHz, ): δ = 147.95 (C-15), 147.47 (C-14), 137.54 (C-6), 134.76 (C-11), 131.91 (C-12), 127.17 (C-8), 125.57 (C-1), 125.14 (C-9), 124.10 (C-13), 122.37 (C-5), 120.38 (C-2), 120.31 (C-4), 119.93 (C-10), 114.02 (C-7), 112.45 (C-3) C 81.79,H 5.49,N 12.72;found: C 81.58,H 5.79,]-1H-indole (5) Following GPA from gramine (5.25 g, 30 mmol), acetonitrile (75 mL), n-PBu 3 (12 mL, 46 mmol) and 4-pyridinecarbaldehyde (4.2 mL, 45 mmol), followed by chromatography (SiO 2 ; hexanes/ethyl acetate, 1:1), 3 (4.31 g, 65%) was obtained as a reddish solid [37,[46][47][48][49][50][51]: R f = 0.26 (SiO 2 , hexanes/ethyl acetate, 1:1); m.p. = 254-255 • C (lit.…”

“…IC 50 values in the single-digit or even sub-nanomolar nanomolar concentration range could be obtained with relatively high selectivity between malignant and non-malignant cells. Depending on the triterpene carboxylic acid used (or its degree of hydroxylation/acetylation), 2,3,23-tris-acetylated triterpene carboxylic acid derivatives interact preferentially with mitochondrial membranes with the almost complete shutdown of mitochondrial ATP synthesis, whereas with mono-acetylated analogues the conjugates could also be detected in the cell nucleus in some cases [ 4 , 5 , 6 ].…”

Can Asiatic Acid from Centella asiatica Be a Potential Remedy in Cancer Therapy?—A Review

“…A study from 2023 conducted by Heise et al investigated how synthetized 1,5diazacyclooctane-spacered triterpene rhodamine conjugates affected breast cancer cells. As the experimental triterpenoic acids, they used oleanolic acid, ursolic acid, betulinic acid, platanic acid, and finally asiatic acid, sourced from C. asiatica [30]. The findings surrounding asiatic acid interested us the most, because it turned out that the AA-rhodamine conjugate demonstrated the most cytotoxic activity of any of the conjugates in all breast cancer cell lines.…”

“…It appears that the conjugate acts as a mitocan (compound targeting mitochondria as the final target [31]). At lower doses, it results in inhibition of proliferation, or growth arrest, in breast cancer cells, and at higher doses it induces apoptosis [30].…”

“…However, we cannot ignore the fact that the cell line HS578T (basal, triple-negative breast cancer cells) turned out to be the most resistant to rhodamine conjugates [30]. That would mean that we have a great base for further research, but it would be worth looking into why some cell lines are less sensitive to the effects of conjugates and where these limitations come from.…”