Herbicidins are isolated from different strains of Streptomyces, and they exhibit several interesting biological activities.1–5 Herbicidins A and B indicated no activity at a concentration of 100 μg mL −1 against Xanthomonas oryzae in vitro, but protection of the leaves of rice plant from bacterial leaf blight disease was caused by X. oryzae. 1 Herbicidins A and B have also been shown to reduce seed germination1 and although they exhibit selective toxicity toward dicotyledonous plants, no toxicity against animals is observed.1 In our effort to search for new biological compounds from endophytes, a new antibiotic 8′-epimer of herbicidin F (1), along with four known compounds, herbicidin F (2),5 herbicidin A (3),5 herbicidin B (4)5–7 and 2′-O-demethylherbicidin F (5)8 were isolated from the broth of Streptomyces sp. YIM 66142, a Dendrobium chrysotoxum endophyte (Figure 1). The absolute configuration of the 8′-epimer of herbicidin F (1) was established using its electronic CD (ECD) spectrum, density functional theory (DFT)-ECD calculations and NOESY spectrum. An antibiotic activity assay showed that herbicidin B (4) and 2′-O-demethylherbicidin F (5) had antibacterial activity against Bacillus subtilis as well as their inhibition of germination of the plant seeds, such as cabbage.