Geographic Influence and Metabolomics-Driven Discovery of 5-Alpha Reductase Inhibitors in Tectona grandis L.f. (Teak) Leaves

Abstract

The inhibition of steroid 5-alpha reductase (S5AR), a key mechanism for managing dihydrotestosterone-dependent conditions, has been demonstrated in teak (Tectona grandis L.f.) leaf extracts. Our recent clinical study confirmed the effectiveness of a hair growth formulation containing teak leaf extract in males with androgenic alopecia. However, significant variability in S5AR inhibitory activity among teak leaf samples from different regions underscores the need for quality control of raw materials. This study applied a metabolomics approach to investigate the influence of leaf age, harvesting period, and geographic origin on chemical composition and S5AR inhibitory activity, as well as to identify active S5AR inhibitors. Geographic origin emerged as the primary determinant of variations in chemical profiles and S5AR inhibitory activity. Using orthogonal partial least squares analysis, six diterpenoid S5AR inhibitors were identified, including four compounds reported for the first time as S5AR inhibitors: rhinocerotinoic acid, 7-oxo-8-labden-15-oic acid, 8-hydroxy-labd-13-en-15-oic acid, and a novel diterpene, 7-hydroxy-labd-8,13-dien-15-oic acid. These findings highlight the potential of metabolomics as a powerful tool for discovering bioactive compounds and optimizing raw material selection. By prioritizing proven geographic sources, consistent bioactivity can be achieved, supporting the therapeutic potential of teak leaves in managing S5AR-related conditions.

Keywords: Tectona grandis L.f.; metabolomics; steroid 5-alpha reductase inhibitor; structure elucidation.

Figure 1

Steroid 5-alpha reductase inhibitory activities of young leaf (YL) and mature leaf (ML) samples collected from 14 provinces in Thailand, classified into four regions: north, central, northeast, and south. The samples were collected in October 2019, December 2019, April–May 2020, and July 2020. The results are presented as the means of triplicate experiments ± standard deviation (SD).

Figure 2

Score plots of PCA. (a) Teak leaf samples harvested in October 2019, classified by leaf age. (b) Young leaves harvested across all years, classified by regions. (c) Young leaves harvested across all years, classified by harvesting periods.

Figure 3

The OPLS plots of teak leaf extracts (young leaves harvested from 14 sources across four batches). (a) The score plot represents the correlation between the samples and their S5AR inhibitory activity. The color gradient indicates the levels of S5AR inhibitory activity. (b) The S-plot represents the chemical compositions responsible for the discrimination of samples in the score plot. The red highlights indicate the candidate S5AR inhibitors.

Figure 4

Stacked bar chart representing % relative distribution of candidate features (F1–F11) detected in teak leaf samples across four geographical regions.

Figure 5

Chemical structures of candidate S5AR inhibitors from teak leaf extract, corresponding to features pinpointed by S-plot analysis of OPLS.

Figure 6

(a) Main COSY and HMBC correlations of 3; (b) main NOESY correlations of 3.

Figure 7

Optimized structures of 3 using B3LYP/6-311++G(d,p) theoretical level.

Figure 8

Experimental and calculated ECD spectra of 3.